review process of research paper

The peer review process

The peer review process can be broadly summarized into 10 steps, although these steps can vary slightly between journals. Explore what’s involved, below.

Editor Feedback: “Reviewers should remember that they are representing the readers of the journal. Will the readers of this particular journal find this informative and useful?”

1. Submission of Paper

The corresponding or submitting author submits the paper to the journal. This is usually via an online system such as ScholarOne Manuscripts. Occasionally, journals may accept submissions by email.

2. Editorial Office Assessment

The Editorial Office checks that the paper adheres to the requirements described in the journal’s Author Guidelines. The quality of the paper is not assessed at this point.

3. Appraisal by the Editor-in-Chief (EIC)

The EIC checks assesses the paper, considering its scope, originality and merits. The EiC may reject the paper at this stage.

4. EIC Assigns an Associate Editor (AE)

Some journals have Associate Editors ( or equivalent ) who handle the peer review. If they do, they would be assigned at this stage.

5. Invitation to Reviewers

The handling editor sends invitations to individuals he or she believes would be appropriate reviewers. As responses are received, further invitations are issued, if necessary, until the required number of reviewers is secured– commonly this is 2, but there is some variation between journals.

6. Response to Invitations

Potential reviewers consider the invitation against their own expertise, conflicts of interest and availability. They then accept or decline the invitation to review. If possible, when declining, they might also suggest alternative reviewers.

7. Review is Conducted

The reviewer sets time aside to read the paper several times. The first read is used to form an initial impression of the work. If major problems are found at this stage, the reviewer may feel comfortable rejecting the paper without further work. Otherwise, they will read the paper several more times, taking notes to build a detailed point-by-point review. The review is then submitted to the journal, with the reviewer’s recommendation (e.g. to revise, accept or reject the paper).

8. Journal Evaluates the Reviews

The handling editor considers all the returned reviews before making a decision. If the reviews differ widely, the editor may invite an additional reviewer so as to get an extra opinion before making a decision.

9. The Decision is Communicated

The editor sends a decision email to the author including any relevant reviewer comments. Comments will be anonymous if the journal follows a single-anonymous or double-anonymous peer review model. Journals with following an open or transparent peer review model will share the identities of the reviewers with the author(s).

10. Next Steps

An editor's perspective.

Listen to a podcast from Roger Watson, Editor-in-Chief of Journal of Advanced Nursing, as he discusses 'The peer review process'.

If accepted , the paper is sent to production. If the article is rejected or sent back for either major or minor revision , the handling editor should include constructive comments from the reviewers to help the author improve the article. At this point, reviewers should also be sent an email or letter letting them know the outcome of their review. If the paper was sent back for revision , the reviewers should expect to receive a new version, unless they have opted out of further participation. However, where only minor changes were requested this follow-up review might be done by the handling editor.

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• What Is Peer Review? | Types & Examples

What Is Peer Review? | Types & Examples

Published on December 17, 2021 by Tegan George . Revised on June 22, 2023.

Peer review, sometimes referred to as refereeing , is the process of evaluating submissions to an academic journal. Using strict criteria, a panel of reviewers in the same subject area decides whether to accept each submission for publication.

Peer-reviewed articles are considered a highly credible source due to the stringent process they go through before publication.

There are various types of peer review. The main difference between them is to what extent the authors, reviewers, and editors know each other’s identities. The most common types are:

• Single-blind review
• Double-blind review
• Triple-blind review

Collaborative review

Open review.

Relatedly, peer assessment is a process where your peers provide you with feedback on something you’ve written, based on a set of criteria or benchmarks from an instructor. They then give constructive feedback, compliments, or guidance to help you improve your draft.

Table of contents

What is the purpose of peer review, types of peer review, the peer review process, providing feedback to your peers, peer review example, advantages of peer review, criticisms of peer review, other interesting articles, frequently asked questions about peer reviews.

Many academic fields use peer review, largely to determine whether a manuscript is suitable for publication. Peer review enhances the credibility of the manuscript. For this reason, academic journals are among the most credible sources you can refer to.

However, peer review is also common in non-academic settings. The United Nations, the European Union, and many individual nations use peer review to evaluate grant applications. It is also widely used in medical and health-related fields as a teaching or quality-of-care measure.

Peer assessment is often used in the classroom as a pedagogical tool. Both receiving feedback and providing it are thought to enhance the learning process, helping students think critically and collaboratively.

Prevent plagiarism. Run a free check.

Depending on the journal, there are several types of peer review.

Single-blind peer review

The most common type of peer review is single-blind (or single anonymized) review . Here, the names of the reviewers are not known by the author.

While this gives the reviewers the ability to give feedback without the possibility of interference from the author, there has been substantial criticism of this method in the last few years. Many argue that single-blind reviewing can lead to poaching or intellectual theft or that anonymized comments cause reviewers to be too harsh.

Double-blind peer review

In double-blind (or double anonymized) review , both the author and the reviewers are anonymous.

Arguments for double-blind review highlight that this mitigates any risk of prejudice on the side of the reviewer, while protecting the nature of the process. In theory, it also leads to manuscripts being published on merit rather than on the reputation of the author.

Triple-blind peer review

While triple-blind (or triple anonymized) review —where the identities of the author, reviewers, and editors are all anonymized—does exist, it is difficult to carry out in practice.

Proponents of adopting triple-blind review for journal submissions argue that it minimizes potential conflicts of interest and biases. However, ensuring anonymity is logistically challenging, and current editing software is not always able to fully anonymize everyone involved in the process.

In collaborative review , authors and reviewers interact with each other directly throughout the process. However, the identity of the reviewer is not known to the author. This gives all parties the opportunity to resolve any inconsistencies or contradictions in real time, and provides them a rich forum for discussion. It can mitigate the need for multiple rounds of editing and minimize back-and-forth.

Collaborative review can be time- and resource-intensive for the journal, however. For these collaborations to occur, there has to be a set system in place, often a technological platform, with staff monitoring and fixing any bugs or glitches.

Lastly, in open review , all parties know each other’s identities throughout the process. Often, open review can also include feedback from a larger audience, such as an online forum, or reviewer feedback included as part of the final published product.

While many argue that greater transparency prevents plagiarism or unnecessary harshness, there is also concern about the quality of future scholarship if reviewers feel they have to censor their comments.

In general, the peer review process includes the following steps:

• First, the author submits the manuscript to the editor.
• Reject the manuscript and send it back to the author, or
• Send it onward to the selected peer reviewer(s)
• Next, the peer review process occurs. The reviewer provides feedback, addressing any major or minor issues with the manuscript, and gives their advice regarding what edits should be made.
• Lastly, the edited manuscript is sent back to the author. They input the edits and resubmit it to the editor for publication.

In an effort to be transparent, many journals are now disclosing who reviewed each article in the published product. There are also increasing opportunities for collaboration and feedback, with some journals allowing open communication between reviewers and authors.

It can seem daunting at first to conduct a peer review or peer assessment. If you’re not sure where to start, there are several best practices you can use.

Summarize the argument in your own words

Summarizing the main argument helps the author see how their argument is interpreted by readers, and gives you a jumping-off point for providing feedback. If you’re having trouble doing this, it’s a sign that the argument needs to be clearer, more concise, or worded differently.

If the author sees that you’ve interpreted their argument differently than they intended, they have an opportunity to address any misunderstandings when they get the manuscript back.

Separate your feedback into major and minor issues

It can be challenging to keep feedback organized. One strategy is to start out with any major issues and then flow into the more minor points. It’s often helpful to keep your feedback in a numbered list, so the author has concrete points to refer back to.

Major issues typically consist of any problems with the style, flow, or key points of the manuscript. Minor issues include spelling errors, citation errors, or other smaller, easy-to-apply feedback.

Tip: Try not to focus too much on the minor issues. If the manuscript has a lot of typos, consider making a note that the author should address spelling and grammar issues, rather than going through and fixing each one.

The best feedback you can provide is anything that helps them strengthen their argument or resolve major stylistic issues.

Give the type of feedback that you would like to receive

No one likes being criticized, and it can be difficult to give honest feedback without sounding overly harsh or critical. One strategy you can use here is the “compliment sandwich,” where you “sandwich” your constructive criticism between two compliments.

Be sure you are giving concrete, actionable feedback that will help the author submit a successful final draft. While you shouldn’t tell them exactly what they should do, your feedback should help them resolve any issues they may have overlooked.

As a rule of thumb, your feedback should be:

• Easy to understand
• Constructive

Below is a brief annotated research example. You can view examples of peer feedback by hovering over the highlighted sections.

Influence of phone use on sleep

Studies show that teens from the US are getting less sleep than they were a decade ago (Johnson, 2019) . On average, teens only slept for 6 hours a night in 2021, compared to 8 hours a night in 2011. Johnson mentions several potential causes, such as increased anxiety, changed diets, and increased phone use.

The current study focuses on the effect phone use before bedtime has on the number of hours of sleep teens are getting.

For this study, a sample of 300 teens was recruited using social media, such as Facebook, Instagram, and Snapchat. The first week, all teens were allowed to use their phone the way they normally would, in order to obtain a baseline.

The sample was then divided into 3 groups:

• Group 1 was not allowed to use their phone before bedtime.
• Group 2 used their phone for 1 hour before bedtime.
• Group 3 used their phone for 3 hours before bedtime.

All participants were asked to go to sleep around 10 p.m. to control for variation in bedtime . In the morning, their Fitbit showed the number of hours they’d slept. They kept track of these numbers themselves for 1 week.

Two independent t tests were used in order to compare Group 1 and Group 2, and Group 1 and Group 3. The first t test showed no significant difference ( p > .05) between the number of hours for Group 1 ( M = 7.8, SD = 0.6) and Group 2 ( M = 7.0, SD = 0.8). The second t test showed a significant difference ( p < .01) between the average difference for Group 1 ( M = 7.8, SD = 0.6) and Group 3 ( M = 6.1, SD = 1.5).

This shows that teens sleep fewer hours a night if they use their phone for over an hour before bedtime, compared to teens who use their phone for 0 to 1 hours.

Peer review is an established and hallowed process in academia, dating back hundreds of years. It provides various fields of study with metrics, expectations, and guidance to ensure published work is consistent with predetermined standards.

• Protects the quality of published research

Peer review can stop obviously problematic, falsified, or otherwise untrustworthy research from being published. Any content that raises red flags for reviewers can be closely examined in the review stage, preventing plagiarized or duplicated research from being published.

• Gives you access to feedback from experts in your field

Peer review represents an excellent opportunity to get feedback from renowned experts in your field and to improve your writing through their feedback and guidance. Experts with knowledge about your subject matter can give you feedback on both style and content, and they may also suggest avenues for further research that you hadn’t yet considered.

• Helps you identify any weaknesses in your argument

Peer review acts as a first defense, helping you ensure your argument is clear and that there are no gaps, vague terms, or unanswered questions for readers who weren’t involved in the research process. This way, you’ll end up with a more robust, more cohesive article.

While peer review is a widely accepted metric for credibility, it’s not without its drawbacks.

• Reviewer bias

The more transparent double-blind system is not yet very common, which can lead to bias in reviewing. A common criticism is that an excellent paper by a new researcher may be declined, while an objectively lower-quality submission by an established researcher would be accepted.

• Delays in publication

The thoroughness of the peer review process can lead to significant delays in publishing time. Research that was current at the time of submission may not be as current by the time it’s published. There is also high risk of publication bias , where journals are more likely to publish studies with positive findings than studies with negative findings.

• Risk of human error

By its very nature, peer review carries a risk of human error. In particular, falsification often cannot be detected, given that reviewers would have to replicate entire experiments to ensure the validity of results.

If you want to know more about statistics , methodology , or research bias , make sure to check out some of our other articles with explanations and examples.

• Normal distribution
• Measures of central tendency
• Chi square tests
• Confidence interval
• Quartiles & Quantiles
• Cluster sampling
• Stratified sampling
• Thematic analysis
• Discourse analysis
• Cohort study
• Ethnography

Research bias

• Implicit bias
• Cognitive bias
• Conformity bias
• Hawthorne effect
• Availability heuristic
• Attrition bias
• Social desirability bias

Peer review is a process of evaluating submissions to an academic journal. Utilizing rigorous criteria, a panel of reviewers in the same subject area decide whether to accept each submission for publication. For this reason, academic journals are often considered among the most credible sources you can use in a research project– provided that the journal itself is trustworthy and well-regarded.

In general, the peer review process follows the following steps: 

• Reject the manuscript and send it back to author, or 
• Send it onward to the selected peer reviewer(s) 
• Next, the peer review process occurs. The reviewer provides feedback, addressing any major or minor issues with the manuscript, and gives their advice regarding what edits should be made. 
• Lastly, the edited manuscript is sent back to the author. They input the edits, and resubmit it to the editor for publication.

Peer review can stop obviously problematic, falsified, or otherwise untrustworthy research from being published. It also represents an excellent opportunity to get feedback from renowned experts in your field. It acts as a first defense, helping you ensure your argument is clear and that there are no gaps, vague terms, or unanswered questions for readers who weren’t involved in the research process.

Peer-reviewed articles are considered a highly credible source due to this stringent process they go through before publication.

Many academic fields use peer review , largely to determine whether a manuscript is suitable for publication. Peer review enhances the credibility of the published manuscript.

However, peer review is also common in non-academic settings. The United Nations, the European Union, and many individual nations use peer review to evaluate grant applications. It is also widely used in medical and health-related fields as a teaching or quality-of-care measure. 

A credible source should pass the CRAAP test  and follow these guidelines:

• The information should be up to date and current.
• The author and publication should be a trusted authority on the subject you are researching.
• The sources the author cited should be easy to find, clear, and unbiased.
• For a web source, the URL and layout should signify that it is trustworthy.

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George, T. (2023, June 22). What Is Peer Review? | Types & Examples. Scribbr. Retrieved September 10, 2024, from https://www.scribbr.com/methodology/peer-review/

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Understanding Peer Review in Science

Peer review is an essential element of the scientific publishing process that helps ensure that research articles are evaluated, critiqued, and improved before release into the academic community. Take a look at the significance of peer review in scientific publications, the typical steps of the process, and and how to approach peer review if you are asked to assess a manuscript.

What Is Peer Review?

Peer review is the evaluation of work by peers, who are people with comparable experience and competency. Peers assess each others’ work in educational settings, in professional settings, and in the publishing world. The goal of peer review is improving quality, defining and maintaining standards, and helping people learn from one another.

In the context of scientific publication, peer review helps editors determine which submissions merit publication and improves the quality of manuscripts prior to their final release.

Types of Peer Review for Manuscripts

There are three main types of peer review:

• Single-blind review: The reviewers know the identities of the authors, but the authors do not know the identities of the reviewers.
• Double-blind review: Both the authors and reviewers remain anonymous to each other.
• Open peer review: The identities of both the authors and reviewers are disclosed, promoting transparency and collaboration.

There are advantages and disadvantages of each method. Anonymous reviews reduce bias but reduce collaboration, while open reviews are more transparent, but increase bias.

Key Elements of Peer Review

Proper selection of a peer group improves the outcome of the process:

• Expertise : Reviewers should possess adequate knowledge and experience in the relevant field to provide constructive feedback.
• Objectivity : Reviewers assess the manuscript impartially and without personal bias.
• Confidentiality : The peer review process maintains confidentiality to protect intellectual property and encourage honest feedback.
• Timeliness : Reviewers provide feedback within a reasonable timeframe to ensure timely publication.

Steps of the Peer Review Process

The typical peer review process for scientific publications involves the following steps:

• Submission : Authors submit their manuscript to a journal that aligns with their research topic.
• Editorial assessment : The journal editor examines the manuscript and determines whether or not it is suitable for publication. If it is not, the manuscript is rejected.
• Peer review : If it is suitable, the editor sends the article to peer reviewers who are experts in the relevant field.
• Reviewer feedback : Reviewers provide feedback, critique, and suggestions for improvement.
• Revision and resubmission : Authors address the feedback and make necessary revisions before resubmitting the manuscript.
• Final decision : The editor makes a final decision on whether to accept or reject the manuscript based on the revised version and reviewer comments.
• Publication : If accepted, the manuscript undergoes copyediting and formatting before being published in the journal.

Pros and Cons

While the goal of peer review is improving the quality of published research, the process isn’t without its drawbacks.

• Quality assurance : Peer review helps ensure the quality and reliability of published research.
• Error detection : The process identifies errors and flaws that the authors may have overlooked.
• Credibility : The scientific community generally considers peer-reviewed articles to be more credible.
• Professional development : Reviewers can learn from the work of others and enhance their own knowledge and understanding.
• Time-consuming : The peer review process can be lengthy, delaying the publication of potentially valuable research.
• Bias : Personal biases of reviews impact their evaluation of the manuscript.
• Inconsistency : Different reviewers may provide conflicting feedback, making it challenging for authors to address all concerns.
• Limited effectiveness : Peer review does not always detect significant errors or misconduct.
• Poaching : Some reviewers take an idea from a submission and gain publication before the authors of the original research.

Steps for Conducting Peer Review of an Article

Generally, an editor provides guidance when you are asked to provide peer review of a manuscript. Here are typical steps of the process.

• Accept the right assignment: Accept invitations to review articles that align with your area of expertise to ensure you can provide well-informed feedback.
• Manage your time: Allocate sufficient time to thoroughly read and evaluate the manuscript, while adhering to the journal’s deadline for providing feedback.
• Read the manuscript multiple times: First, read the manuscript for an overall understanding of the research. Then, read it more closely to assess the details, methodology, results, and conclusions.
• Evaluate the structure and organization: Check if the manuscript follows the journal’s guidelines and is structured logically, with clear headings, subheadings, and a coherent flow of information.
• Assess the quality of the research: Evaluate the research question, study design, methodology, data collection, analysis, and interpretation. Consider whether the methods are appropriate, the results are valid, and the conclusions are supported by the data.
• Examine the originality and relevance: Determine if the research offers new insights, builds on existing knowledge, and is relevant to the field.
• Check for clarity and consistency: Review the manuscript for clarity of writing, consistent terminology, and proper formatting of figures, tables, and references.
• Identify ethical issues: Look for potential ethical concerns, such as plagiarism, data fabrication, or conflicts of interest.
• Provide constructive feedback: Offer specific, actionable, and objective suggestions for improvement, highlighting both the strengths and weaknesses of the manuscript. Don’t be mean.
• Organize your review: Structure your review with an overview of your evaluation, followed by detailed comments and suggestions organized by section (e.g., introduction, methods, results, discussion, and conclusion).
• Be professional and respectful: Maintain a respectful tone in your feedback, avoiding personal criticism or derogatory language.
• Proofread your review: Before submitting your review, proofread it for typos, grammar, and clarity.
• Couzin-Frankel J (September 2013). “Biomedical publishing. Secretive and subjective, peer review proves resistant to study”. Science . 341 (6152): 1331. doi: 10.1126/science.341.6152.1331
• Lee, Carole J.; Sugimoto, Cassidy R.; Zhang, Guo; Cronin, Blaise (2013). “Bias in peer review”. Journal of the American Society for Information Science and Technology. 64 (1): 2–17. doi: 10.1002/asi.22784
• Slavov, Nikolai (2015). “Making the most of peer review”. eLife . 4: e12708. doi: 10.7554/eLife.12708
• Spier, Ray (2002). “The history of the peer-review process”. Trends in Biotechnology . 20 (8): 357–8. doi: 10.1016/S0167-7799(02)01985-6
• Squazzoni, Flaminio; Brezis, Elise; Marušić, Ana (2017). “Scientometrics of peer review”. Scientometrics . 113 (1): 501–502. doi: 10.1007/s11192-017-2518-4

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• Published: 12 November 2021

Demystifying the process of scholarly peer-review: an autoethnographic investigation of feedback literacy of two award-winning peer reviewers

• Sin Wang Chong   ORCID: orcid.org/0000-0002-4519-0544 1 &
• Shannon Mason 2  

Humanities and Social Sciences Communications volume  8 , Article number:  266 ( 2021 ) Cite this article

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A Correction to this article was published on 26 November 2021

This article has been updated

Peer reviewers serve a vital role in assessing the value of published scholarship and improving the quality of submitted manuscripts. To provide more appropriate and systematic support to peer reviewers, especially those new to the role, this study documents the feedback practices and experiences of two award-winning peer reviewers in the field of education. Adopting a conceptual framework of feedback literacy and an autoethnographic-ecological lens, findings shed light on how the two authors design opportunities for feedback uptake, navigate responsibilities, reflect on their feedback experiences, and understand journal standards. Informed by ecological systems theory, the reflective narratives reveal how they unravel the five layers of contextual influences on their feedback practices as peer reviewers (micro, meso, exo, macro, chrono). Implications related to peer reviewer support are discussed and future research directions are proposed.

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What matters in the cultivation of student feedback literacy: exploring university efl teachers’ perceptions and practices, why english exploring chinese early career returnee academics’ motivations for writing and publishing in english, introduction.

The peer-review process is the longstanding method by which research quality is assured. On the one hand, it aims to assess the quality of a manuscript, with the desired outcome being (in theory if not always in practice) that only research that has been conducted according to methodological and ethical principles be published in reputable journals and other dissemination outlets (Starck, 2017 ). On the other hand, it is seen as an opportunity to improve the quality of manuscripts, as peers identify errors and areas of weakness, and offer suggestions for improvement (Kelly et al., 2014 ). Whether or not peer review is actually successful in these areas is open to considerable debate, but in any case it is the “critical juncture where scientific work is accepted for publication or rejected” (Heesen and Bright, 2020 , p. 2). In contemporary academia, where higher education systems across the world are contending with decreasing levels of public funding, there is increasing pressure on researchers to be ‘productive’, which is largely measured by the number of papers published, and of funding grants awarded (Kandiko, 2010 ), both of which involve peer review.

Researchers are generally invited to review manuscripts once they have established themselves in their disciplinary field through publication of their own research. This means that for early career researchers (ECRs), their first exposure to the peer-review process is generally as an author. These early experiences influence the ways ECRs themselves conduct peer review. However, negative experiences can have a profound and lasting impact on researchers’ professional identity. This appears to be particularly true when feedback is perceived to be unfair, with feedback tone largely shaping author experience (Horn, 2016 ). In most fields, reviewers remain anonymous to ensure freedom to give honest and critical feedback, although there are concerns that a lack of accountability can result in ‘bad’ and ‘rude’ reviews (Mavrogenis et al., 2020 ). Such reviews can negatively impact all researchers, but disproportionately impact underrepresented researchers (Silbiger and Stubler, 2019 ). Regardless of career phase, no one is served well by unprofessional reviews, which contribute to the ongoing problem of bullying and toxicity prevalent in academia, with serious implications on the health and well-being of researchers (Keashly and Neuman, 2010 ).

Because of its position as the central process through which research is vetted and refined, peer review should play a similarly central role in researcher training, although it rarely features. In surveying almost 3000 researchers, Warne ( 2016 ) found that support for reviewers was mostly received “in the form of journal guidelines or informally as advice from supervisors or colleagues” (p. 41), with very few engaging in formal training. Among more than 1600 reviewers of 41 nursing journals, only one third received any form of support (Freda et al., 2009 ), with participants across both of these studies calling for further training. In light of the lack of widespread formal training, most researchers learn ‘on the job’, and little is known about how researchers develop their knowledge and skills in providing effective assessment feedback to their peers. In this study, we undertake such an investigation, by drawing on our first-hand experiences. Through a collaborative and reflective process, we look to identify the forms and forces of our feedback literacy development, and seek to answer specifically the following research questions:

What are the exhibited features of peer reviewer feedback literacy?

What are the forces at work that affect the development of feedback literacy?

Literature review

Conceptualisation of feedback literacy.

The notion of feedback literacy originates from the research base of new literacy studies, which examines ‘literacies’ from a sociocultural perspective (Gee, 1999 ; Street, 1997 ). In the educational context, one of the most notable types of literacy is assessment literacy (Stiggins, 1999 ). Traditionally, assessment literacy is perceived as one of the indispensable qualities of a successful educator, which refers to the skills and knowledge for teachers “to deal with the new world of assessment” (Fulcher, 2012 , p. 115). Following this line of teacher-oriented assessment literacy, recent attempts have been made to develop more subject-specific assessment literacy constructs (e.g., Levi and Inbar-Lourie, 2019 ). Given the rise of student-centred approaches and formative assessment in higher education, researchers began to make the case for students to be ‘assessment literate’; comprising of such knowledge and skills as understanding of assessment standards, the relationship between assessment and learning, peer assessment, and self-assessment skills (Price et al., 2012 ). Feedback literacy, as argued by Winstone and Carless ( 2019 ), is essentially a subset of assessment literacy because “part of learning through assessment is using feedback to calibrate evaluative judgement” (p. 24). The notion of feedback literacy was first extensively discussed by Sutton ( 2012 ) and more recently by Carless and Boud ( 2018 ). Focusing on students’ feedback literacy, Sutton ( 2012 ) conceptualised feedback literacy as a three-dimensional construct—an epistemological dimension (what do I know about feedback?), an ontological dimension (How capable am I to understand feedback?), and a practical dimension (How can I engage with feedback?). In close alignment with Sutton’s construct, the seminal conceptual paper by Carless and Boud ( 2018 ) further illustrated the four distinctive abilities of feedback literate students: the abilities to (1) understand the formative role of feedback, (2) make informed and accurate evaluative judgement against standards, (3) manage emotions especially in the face of critical and harsh feedback, and (4) take action based on feedback. Since the publication of Carless and Boud ( 2018 ), student and teacher feedback literacy has been in the limelight of assessment research in higher education (e.g., Chong 2021b ; Carless and Winstone 2020 ). These conceptual contributions expand the notion of feedback literacy to consider not only the manifestations of various forms of effective student engagement with feedback but also the confluence of contexts and individual differences of students in developing students’ feedback literacy by drawing upon various theoretical perspectives (e.g., ecological systems theory; sociomaterial perspective) and disciplines (e.g., business and human resource management). Others address practicalities of feedback literacy; for example, how teachers and students can work in synergy to develop feedback literacy (Carless and Winstone, 2020 ) and ways to maximise student engagement with feedback at a curricular level (Malecka et al., 2020). In addition to conceptualisation, advancement of the notion of feedback literacy is evident in the recent proliferation of primary studies. The majority of these studies are conducted in the field of higher education, focusing mostly on student feedback literacy in classrooms (e.g., Molloy et al., 2019 ; Winstone et al., 2019 ) and in the workplace (Noble et al., 2020 ), with a handful focused on teacher feedback literacy (e.g., Xu and Carless 2016 ). Some studies focusing on student feedback literacy adopt a qualitative case study research design to delve into individual students’ experience of engaging with various forms of feedback. For example, Han and Xu ( 2019 ) analysed the profiles of feedback literacy of two Chinese undergraduate students. Findings uncovered students’ resistance to engagement with feedback, which relates to the misalignment between the cognitive, social, and affective components of individual students’ feedback literacy profiles. Others reported interventions designed to facilitate students’ uptake of feedback, focusing on their effectiveness and students’ perceptions. Specifically, affordances and constraints of educational technology such as electronic feedback portfolio (Chong, 2019 ; Winstone et al., 2019 ) are investigated. Of particular interest is a recent study by Noble et al. ( 2020 ), which looked into student feedback literacy in the workplace by probing into the perceptions of a group of Australian healthcare students towards a feedback literacy training programme conducted prior to their placement. There is, however, a dearth of primary research in other areas where elicitation, process, and enactment of feedback are vital; for instance, academics’ feedback literacy. In the ‘publish or perish’ culture of higher education, academics, especially ECRs, face immense pressure to publish in top-tiered journals in their fields and face the daunting peer-review process, while juggling other teaching and administrative responsibilities (Hollywood et al., 2019 ; Tynan and Garbett 2007 ). Taking up the role of authors and reviewers, researchers have to possess the capacity and disposition to engage meaningfully with feedback provided by peer reviewers and to provide constructive comments to authors. Similar to students, researchers have to learn how to manage their emotions in the face of critical feedback, to understand the formative values of feedback, and to make informed judgements about the quality of feedback (Gravett et al., 2019 ). At the same time, feedback literacy of academics also resembles that of teachers. When considering the kind of feedback given to authors, academics who serve as peer reviewers have to (1) design opportunities for feedback uptake, (2) maintain a professional and supportive relationship with authors, and (3) take into account the practical dimension of giving feedback (e.g., how to strike a balance between quality of feedback and time constraints due to multiple commitments) (Carless and Winstone 2020 ). To address the above, one of the aims of the present study is to expand the application of feedback literacy as a useful analytical lens to areas outside the classroom, that is, scholarly peer-review activities in academia, by presenting, analysing, and synthesising the personal experiences of the authors as successful peer reviewers for academic journals.

Conceptual framework

We adopt a feedback literacy of peer reviewers framework (Chong 2021a ) as an analytical lens to analyse, systemise, and synthesise our own experiences and practices as scholarly peer reviewers (Fig. 1 ). This two-tier framework includes a dimension on the manifestation of feedback literacy, which categorises five features of feedback literacy of peer reviewers, informed by student and teacher feedback literacy frameworks by Carless and Boud ( 2018 ) and Carless and Winstone ( 2020 ). When engaging in scholarly peer review, reviewers are expected to be able to provide constructive and formative feedback, which authors can act on in their revisions ( engineer feedback uptake ). Besides, peer reviewers who are usually full-time researchers or academics lead hectic professional lives; thus, when writing reviewers’ reports, it is important for them to consider practically and realistically the time they can invest and how their various degrees of commitment may have an impact on the feedback they provide ( navigate responsibilities ). Furthermore, peer reviewers should consider the emotional and relational influences their feedback exert on the authors. It is crucial for feedback to be not only informative but also supportive and professional (Chong, 2018 ) ( maintain relationships ). Equally important, it is imperative for peer reviewers to critically reflect on their own experience in the scholarly peer-review process, including their experience of receiving and giving feedback to academic peers, as well as the ways authors and editors respond to their feedback ( reflect on feedback experienc e). Lastly, acting as gatekeepers of journals to assess the quality of manuscripts, peer reviewers have to demonstrate an accurate understanding of the journals’ aims, remit, guidelines and standards, and reflect those in their written assessments of submitted manuscripts ( understand standards ). Situated in the context of scholarly peer review, this collaborative autoethnographic study conceptualises feedback literacy not only as a set of abilities but also orientations (London and Smither, 2002 ; Steelman and Wolfeld, 2016 ), which refers to academics’ tendency, beliefs, and habits in relation to engaging with feedback (London and Smither, 2002 ). According to Cheung ( 2000 ), orientations are influenced by a plethora of factors, namely experiences, cultures, and politics. It is important to understand feedback literacy as orientations because it takes into account that feedback is a convoluted process and is influenced by a plethora of contextual and personal factors. Informed by ecological systems theory (Bronfenbrenner, 1986 ; Neal and Neal, 2013 ) and synthesising existing feedback literacy models (Carless and Boud, 2018 ; Carless and Winstone, 2020 ; Chong, 2021a , 2021b ), we consider feedback literacy as a malleable, situated, and emergent construct, which is influenced by the interplay of various networked layers of ecological systems (Neal and Neal, 2013 ) (Fig. 1 ). Also important is that conceptualising feedback literacy as orientations avoids dichotomisation (feedback literate vs. feedback illiterate), emphasises the developmental nature of feedback literacy, and better captures the multifaceted manifestations of feedback engagement.

The outer ring of the figure shows the components of feedback literacy while the inner ring concerns the layers of contexts (ecosystems) which influence the manifestation of feedback literacy of peer reviewers.

Echoing recent conceptual papers on feedback literacy which emphasises the indispensable role of contexts (Chong 2021b ; Boud and Dawson, 2021 ; Gravett et al., 2019 ), our conceptual framework includes an underlying dimension of networked ecological systems (micro, meso, exo, macro, and chrono), which portrays the contextual forces shaping our feedback orientations. Informed by the networked ecological system theory of Neal and Neal ( 2013 ), we postulate that there are five systems of contextual influence, which affect the feedback experience and development of feedback literacy of peer reviewers. The five ecological systems refer to ‘settings’, which is defined by Bronfenbrenner ( 1986 ) as “place[s] where people can readily engage in social interactions” (p. 22). Even though Bronfenbrenner’s ( 1986 ) somewhat dated definition of ‘place’ is limited to ‘physical space’, we believe that ‘places’ should be more broadly defined in the 21st century to encompass physical and virtual, recent and dated, closed and distanced locations where people engage; as for ‘interactions’, from a sociocultural perspective, we understand that ‘interactions’ can include not only social, but also cognitive and emotional exchanges (Vygotsky, 1978 ). Microsystem refers to a setting where people, including the focal individual, interact. Mesosystem , on the other hand, means the interactions between people from different settings and the influence they exert on the focal individual. An exosystem , similar to a microsystem, is understood as a single setting but this setting excludes the focal individual but it is likely that participants in this setting would interact with the focal individual. The remaining two systems, macrosystem and chronosystem, refer not only to ‘settings’ but ‘forces that shape the patterns of social interactions that define settings’ (Neal and Neal, 2013 , p. 729). Macrosystem is “the set of social patterns that govern the formation and dissolution of… interactions… and thus the relationship among ecological systems” (ibid). Some examples of macrosystems given by Neal and Neal ( 2013 ) include political and cultural systems. Finally, chronosystem is “the observation that patterns of social interactions between individuals change over time, and that such changes impact on the focal individual” (ibid, p. 729). Figure 2 illustrates this networked ecological systems theory using a hypothetical example of an early career researcher who is involved in scholarly peer review for Journal A; at the same time, they are completing a PhD and are working as a faculty member at a university.

This is a hypothetical example of an early career researcher who is involved in scholarly peer review for Journal A.

From the reviewed literature on the construct of feedback literacy, the investigation of feedback literacy as a personal, situated, and unfolding process is best done through an autoethnographic lens, which underscores critical self-reflection. Autoethnography refers to “an approach to research and writing that seeks to describe and systematically analyse (graphy) personal experience (auto) in order to understand cultural experience (ethno)” (Ellis et al., 2011 , p. 273). Autoethnography stems from research in the field of anthropology and is later introduced to the fields of education by Ellis and Bochner ( 1996 ). In higher education research, autoethnographic studies are conducted to illuminate on topics related to identity and teaching practices (e.g., Abedi Asante and Abubakari, 2020 ; Hains-Wesson and Young 2016 ; Kumar, 2020 ). In this article, a collaborative approach to autoethnography is adopted. Based on Chang et al. ( 2013 ), Lapadat ( 2017 ) defines collaborative autoethnography (CAE) as follows:

… an autobiographic qualitative research method that combines the autobiographic study of self with ethnographic analysis of the sociocultural milieu within which the researchers are situated, and in which the collaborating researchers interact dialogically to analyse and interpret the collection of autobiographic data. (p. 598)

CAE is not only a product but a worldview and process (Wall, 2006 ). CAE is a discrete view about the world and research, which straddles between paradigmatic boundaries of scientific and literary studies. Similar to traditional scientific research, CAE advocates systematicity in the research process and consideration is given to such crucial research issues as reliability, validity, generalisability, and ethics (Lapadat, 2017 ). In closer alignment with studies on humanities and literature, the goal of CAE is not to uncover irrefutable universal truths and generate theories; instead, researchers of CAE are interested in co-constructing and analysing their own personal narratives or ‘stories’ to enrich and/or challenge mainstream beliefs and ideas, embracing diverse rather than canonical ways of behaviour, experience, and thinking (Ellis et al., 2011 ). Regarding the role of researchers, CAE researchers openly acknowledge the influence (and also vulnerability) of researchers throughout the research process and interpret this juxtaposition of identities between researchers and participants of research as conducive to offering an insider’s perspective to illustrate sociocultural phenomena (Sughrua, 2019 ). For our CAE on the scholarly peer-review experiences of two ECRs, the purpose is to reconstruct, analyse, and publicise our lived experience as peer reviewers and how multiple forces (i.e., ecological systems) interact to shape our identity, experience, and feedback practice. As a research process, CAE is a collaborative and dynamic reflective journey towards self-discovery, resulting in narratives, which connect with and add to the existing literature base in a personalised manner (Ellis et al., 2011 ). The collaborators should go beyond personal reflection to engage in dialogues to identify similarities and differences in experiences to throw new light on sociocultural phenomena (Merga et al., 2018 ). The iterative process of self- and collective reflections takes place when CAE researchers write about their own “remembered moments perceived to have significantly impacted the trajectory of a person’s life” and read each other’s stories (Ellis et al., 2011 , p. 275). These ‘moments’ or vignettes are usually written retrospectively, selectively, and systematically to shed light on facets of personal experience (Hughes et al., 2012 ). In addition to personal stories, some autoethnographies and CAEs utilise multiple data sources (e.g., reflective essays, diaries, photographs, interviews with co-researchers) and various ways of expressions (e.g., metaphors) to achieve some sort of triangulation and to present evidence in a ‘systematic’ yet evocative manner (Kumar, 2020 ). One could easily notice that overarching methodological principles are discussed in lieu of a set of rigid and linear steps because the process of reconstructing experience through storytelling can be messy and emergent, and certain degree of flexibility is necessary. However, autoethnographic studies, like other primary studies, address core research issues including reliability (reader’s judgement of the credibility of the narrator), validity (reader’s judgement that the narratives are believable), and generalisability (resemblance between the reader’s experience and the narrative, or enlightenment of the reader regarding unfamiliar cultural practices) (Ellis et al., 2011 ). Ethical issues also need to be considered. For example, authors are expected to be honest in reporting their experiences; to protect the privacy of the people who ‘participated’ in our stories, pseudonyms need to be used (Wilkinson, 2019 ). For the current study, we follow the suggested CAE process outlined by Chang et al. ( 2013 ), which includes four stages: deciding on topic and method , collecting materials , making meaning , and writing . When deciding on the topic, we decided to focus on our experience as scholarly peer reviewers because doing peer review and having our work reviewed are an indispensable part of our academic lives. The next is to collect relevant autoethnographic materials. In this study, we follow Kumar ( 2020 ) to focus on multiple data sources: (1) reflective essays which were written separately through ‘recalling’, which is referred to by Chang et al. ( 2013 ) as ‘a free-spirited way of bringing out memories about critical events, people, place, behaviours, talks, thoughts, perspectives, opinions, and emotions pertaining to the research topic’ (p. 113), and (2) discussion meetings. In our reflective essays, we included written records of reflection and excerpts of feedback in our peer-review reports. Following material collection is meaning making. CAE, as opposed to autoethnography, emphasises the importance of engaging in dialogues with collaborators and through this process we identify similarities and differences in our experiences (Sughrua, 2019 ). To do so, we exchanged our reflective essays; we read each other’s reflections and added questions or comments on the margins. Then, we met online twice to share our experiences and exchange views regarding the two reflective essays we wrote. Both meetings lasted for approximately 90 min, were audio-recorded and transcribed. After each meeting, we coded our stories and experiences with reference to the two dimensions of the ecological framework of feedback literacy (Fig. 1 ). With regards to coding our data, we followed the model of Miles and Huberman ( 1994 ), which comprises four stages: data reduction (abstracting data), data display (visualising data in tabular form), conclusion-drawing, and verification. The coding and writing processes were done collaboratively on Google Docs and care was taken to address the aforesaid ethical (e.g., honesty, privacy) and methodological issues (e.g., validity, reliability, generalisability). As a CAE study, the participants are the researchers themselves, that is, the two authors of this paper. We acknowledge that research data are collected from human subjects (from the two authors), such data are collected in accordance with the standards and guidelines of the School Research Ethics Committee at the School of Social Sciences, Education and Social Work, Queen’s University Belfast (Ref: 005_2021). Despite our different experiences in our unique training and employment contexts, we share some common characteristics, both being ECRs (<5 years post-PhD), working in the field of education, active in the scholarly publication process as both authors and peer reviewers. Importantly for this study, we were both recipients of Reviewer of the Year Award 2019 awarded jointly by the journal, Higher Education Research & Development and the publisher , Taylor & Francis. This award in recognition of the quality of our reviewing efforts, as determined by the editorial board of a prestigious higher education journal, provided a strong impetus for this study, providing an opportunity to reflect on our own experiences and practices. The extent of our peer-review activities during our early career leading up to the time of data collection is summarised in Table 1 .

Findings and discussion

Analysis of the four individual essays (E1 and E2 for each participant) and transcripts of the two subsequent discussions (D1 and D2) resulted in the identification of multiple descriptive codes and in turn a number of overarching themes (Supplementary Appendix 1). Our reporting of these themes is guided by our conceptual framework, where we first focus on the five manifestations of feedback literacy to highlight the experiences that contribute to our growth as effective and confident peer reviewers. Then, we report on the five ecological systems to unravel how each contextual layer develops our feedback literacy as peer reviewers. (Note that the discussion of the chronosystem has been necessarily incorporated into each of the four others dimensions: microsystem , mesosystem , exosystem , and macrosystem in order to demonstrate temporal changes). In particular, similarities and differences will be underscored, and connections with manifested feedback beliefs and behaviours will be made. We include quotes from both Author 1 (A1) and Author 2 (A2), in order to illustrate our findings, and to show the richness and depth of the data collected (Corden and Sainsbury, 2006 ). Transcribed quotes may be lightly edited while retaining meaning, for example through the removal of fillers and repetitions, which is generally accepted practice to ensure readability ( ibid ).

Manifestations of feedback literacy

Engineering feedback uptake.

The two authors have a strong sense of the purpose of peer review as promoting not only research quality, but the growth of researchers. One way that we engineer author uptake is to ensure that feedback is ‘clear’ (A2,E1), ‘explicit’ (A2,E1), ‘specific’ (A1,E1), and importantly ‘actionable… to ensure that authors can act on this feedback so that their manuscripts can be improved and ultimately accepted for publication’ (A1,E1). In less than favourable author outcomes, we ensure that there is reference to the role of the feedback in promoting the development of the manuscript, which A1 refers to as ‘promotion of a growth mindset’ (A1,E1). For example, after requesting a second round of major revisions, A2 ‘acknowledged the frustration that the author might have felt on getting further revisions by noting how much improvement was made to the paper, but also making clear the justification for sending it off for more work’ (A2,E1). We both note that we tend to write longer reviews when a rejection is the recommended outcome, as our ultimate goal is to aid in the development of a manuscript.

Rejections doesn’t mean a paper is beyond repair. It can still be fixed and improved; a rejection simply means that the fix may be too extensive even for multiple review cycles. It is crucial to let the authors whose manuscripts are rejected know that they can still act on the feedback to improve their work; they should not give up on their own work. I think this message is especially important to first-time authors or early career researchers. (A1,E1)

In promoting a growth mindset and in providing actionable feedback, we hope to ‘show the authors that I’m not targeting them, but their work’ (A1,D1). We particularly draw on our own experiences as ECRs, with first-hand understanding that ‘everyone takes it personally when they get rejected. Yeah. Moreover, it is hard to separate (yourself from the paper)’ (A2,D1).

Navigating responsibilities

As with most academics, the two authors have multiple pressures on their time, and there ‘isn’t much formal recognition or reward’ (A1,E1) and ‘little extrinsic incentive for me to review’ (A2,E1). Nevertheless we both view our roles as peer reviewers as ‘an important part of the process’ (A2,E1), ‘a modest way for me to give back to the academic community’ (A1,E1). Through peer review we have built a sense of ‘identity as an academic’ (A1,D1), through ‘being a member of the academic community’ (A2,D1). While A1 commits to ‘review as many papers as possible’ (A1,E1) and A2 will usually accept offers to review, there are still limits on our time and therefore we consider the topic and methods employed when deciding whether or not to accept an invitation, as well as the journal itself, as we feel we can review more efficiently for journals with which we are more familiar. A1 and A2 have different processes for conducting their review that are most efficient for their own situations. For A1, the process begins with reading the whole manuscript in one go, adding notes to the pdf document along the way, which he then reviews, and makes a tentative decision, including ‘a few reasons why I have come to this decision’ (A1,E1). After waiting at least one day, he reviews all of the notes and begins writing the report, which is divided into the sections of the paper. He notes it ‘usually takes me 30–45 min to write a report. I then proofread this report and submit it to the system. So it usually takes me no more than three hours to complete a review’ (A1,E1). For A2, the process for reviewing and structuring the report is quite different, with a need to ‘just find small but regular opportunities to work on the review’ (A2,E1). As was the case during her Ph.D, which involved juggling research and raising two babies, ‘I’ve trained myself to be able to do things in bits’ (A2,D1). So A2 also begins by reading the paper once through, although generally without making initial comments. The next phase involves going through the paper at various points in time whenever possible, and at the same time building up the report, making the report structurally slightly different to that of A1.

What my reviews look like are bullet points, basically. And they’re not really in a particular order. They generally… follow the flow (of the paper). But I mean, I might think of something, looking at the methods and realise, hey, you haven’t defined this concept in the literature review so I’ll just add you haven’t done this. And so I will usually preface (the review)… Here’s a list of suggestions. Some of them are minor, some of them are serious, but they’re in no particular order. (A1,D1)

As such, both reviewers engage in personalised strategies to make more effective use of their time. Both A1 and A2 give explicit but not exhaustive examples of an area of concern, and they also pose questions for the author to consider, in both cases placing the onus back on the author to take action. As A1 notes, ‘I’m not going to do a summary of that reference for you. I’m just going to include that there. If you’d like you can check it out’ (A1,D1). For A2, a lack of adequate reporting of the methods employed in a study makes it difficult to proceed, and in such cases will not invest further time, sending it back to the editor, because ‘I can’t even comment on the findings… I can’t go on. I’m not gonna waste my time’ (A2,D1). In cases where the authors may be ‘on the fence’ about a particular review, they will use the confidential comments to the editor to help work through difficult cases as ‘they are obviously very experienced reviewers’ (A1,D1). Delegating tasks to the expertise of the editorial teams when appropriate also ensures time is used more prudently.

Maintaining relationships

Except in a few cases where A2 has reviewed for journals with a single-blind model, the vast majority of the reviews that we have completed have been double-blind. This means that we are unaware of the identity of the author/s, and we are unknown to them. However, ‘even with blind-reviews I tend to think of it as a conversation with a person’ (A2,E1). A1 talks about the need to have respect for the author and their expertise and effort ‘regardless of the quality of the submission (which can be in some cases subjective)’ (A1,E1). A2 writes similarly about the ‘privilege’ and ‘responsibility’ of being able to review manuscripts that authors ‘have put so much time and energy into possibly over an extended period’ (A2,E1). In this way it is possible to develop a sort of relationship with an author even without knowing their identity. In trying to articulate the nature of that relationship (which we struggle to do so definitively), we note that it is more than just a reviewer, and A2 reflected on a recent review, which went through a number of rounds of resubmission where ‘it felt like we were developing a relationship, more like a mentor than a reviewer’ (A2,E1).

I consider this role as a peer reviewer more than giving helpful and actionable feedback; I would like to be a supporter and critical friend to the authors, even though in most cases I don’t even know who they are or what career stage they are at (A1,E1).

In any case, as A1 notes, ‘we don’t even need to know who that person is because we know that people like encouragement’ (A1,D1), and we are very conscious of the emotional impact that feedback can have on authors, and the inherent power imbalance in the relationship. For this reason, A1 is ‘cautious about the way I write so that I don’t accidentally make the authors the target of my feedback’. As A2 notes ‘I don’t want authors feeling depressed after reading a review’ (A2,E1). While we note that we try to deliver our feedback with ‘respect’ (A1,E1; A1,E2; A2,D1) ‘empathy’ (A1,E1), and ‘kindness’ (A2,D1), we both noted that we do not ‘sugar coat’ our feedback and A1 describes himself as ‘harsh’ and ‘critical’ (A1,E1) while A2 describes herself as ‘pretty direct’ (A2,E1). In our discussion, we tried to delve into this seeming contradiction:… the encouragement, hopefully is to the researcher, but the directness it should be, I hope, is related directly to whatever it is, the methods or the reporting or the scope of the literature review. It’s something specific about the manuscript itself. And I know myself, being an ECR and being reviewed, that it’s hard to separate yourself from your work… And I want to make it really explicit. If it’s critical, it’s not about the person. It’s about the work, you know, the weakness of the work, but not the person. (A2,D1)

A1 explains that at times his initial report may be highly critical, and at times he will ‘sit back and rethink… With empathy, I will write feedback, which is more constructive’ (A1,E1). However, he adds that ‘I will never try to overrate a piece or sugar-coat my comments just to sound “friendly”’ (A1,E1), with the ultimate goal being to uphold academic rigour. Thus, honesty is seen as the best strategy to maintain a strong, professional relationship with reviewers. Another strategy employed by A2 is showing explicit commitment to the review process. One way this is communicated is by prefacing a review with a summary of the paper, not only ‘to confirm with the author that I am interpreting the findings in the way that they intended, but also importantly to show that I have engaged with the paper’ (A2,E1). Further, if the recommendation is for a further round of review, she will state directly to the authors ‘that I would be happy to review a revised manuscript’ (A2,E1).

Reflecting on feedback experience

As ECRs we have engaged in the scholarly publishing process initially as authors, subsequently as reviewers, and most recently as Associate Editors. Insights gained in each of these roles have influenced our feedback practices, and have interacted to ‘develop a more holistic understanding of the whole review process’ (A1,E1).

We reflect on our experiences as authors beginning in our doctoral candidatures, with reviews that ranged from ‘the most helpful to the most cynical’ (A1,E1). A2 reflected on two particular experiences both of which resulted in rejection, one being ‘snarky’ and ‘unprofessional’ with ‘no substance’, the other providing ‘strong encouragement … the focus was clearly on the paper and not me personally’ (A2,E1). It was this experience that showed the divergence between the tone and content of review despite the same outcome, and as result A2 committed to being ‘ the amazing one’. A1 also drew from a negative experience noting that ‘I remember the least useful feedback as much as I do with the most constructive one’ (A1,E1). This was particularly the case when a reviewer made apparently politically-motivated judgements that A1 ‘felt very uncomfortable with’ and flagged with the editor (A1,E1). Through these experiences both authors wrote in their essays about the need to focus on the work and not on the individual, with an understanding that a review ‘can have a really serious impact’ (A2,D1) on an author.

It is important to note that neither authors have been involved in any formal or informal training on how to conduct peer review, although A1 expresses appreciation of the regular practice of one journal for which he reviews, where ‘the editor would write an email to the reviewers giving feedback on the feedback we have given’ (A1,E1). For A2, an important source of learning is in comparing her reviews with that of others who have reviewed the same manuscript, the norm for some journals being to send all reports to all reviewers along with the final decision.

I’m always interested to see how [my] review compares with others. Have I given the same recommendation? Have I identified the same areas of weakness? Have I formatted my review in the same way? How does the tone of delivery differ? I generally find that I give a similar if not the same response to other reviews, and I’m happy to see that I often pick up the same issues with methodology. (A2,E1)

For A2 there is comfort in seeing reviews that are similar to others, although we both draw on experiences where our recommendation diverged from others, with a source of assurance being the ultimate decision of the editor.

So it’s like, I don’t think it can be published and that [other] reviewer thinks it’s excellent. So usually, what the editor would do in this instance is invite the third one. Right, yeah. But then this editor told me… that they decided to go with my decision to reject because they find that my comments are more convincing. (A1,D1)

A2 also was surprised to read another report of the same manuscript she reviewed, that raised similar concerns and gave the same recommendation for major revisions, but noted the ‘wording is soooo snarky. What need?’ (A2,E1). In one case that A1 detailed in our first discussion, significant but improbable changes made to the methodology section of a resubmitted paper caused him to question the honesty of the reporting, making him ‘uncomfortable’ and as a result reported his concerns to the editor. In this case the review took some time to craft, trying to balance the ‘fine line between catering for the emotion [of the author], right, and upholding the academic standards’ (A1,D1). While he conceded initially his report was ‘kind of too harsh… later I think I rephrased it a little bit, I kind of softened (it)’.

While the role of Associate Editor is very new to A2 and thus was yet unable to comment, for A1 the ‘opportunity to read various kinds of comments given by reviewers’ (A1,E1) is viewed favourably. This includes not only how reviewers structure their feedback, but also how they use the confidential comments to the editors to express their thoughts more openly, providing important insights into the process that are largely hidden.

Understanding standards

While our reviewing practices are informed more broadly ‘according to more general academic standards of the study itself, and the clarity and fullness of the reporting’ (A2,E1), we look in the first instance to advice and guidelines from journals to develop an understanding of journal-specific standards, although A2 notes that a lack of review guidelines for one of the earliest journals she reviewed led her to ‘searching Google for standard criteria’ (A2,E1). However, our development in this area seems to come from developing a familiarity with a journal, particularly through engagement with the journal as an author.

In addition to reading the scope and instructions for authors to obtain such basic information as readership, length of submissions, citation style, the best way for me to understand the requirements and preferences of the journals is my own experience as an author. I review for journals which I have published in and for those which I have not. I always find it easier to make a judgement about whether the manuscripts I review meet the journal’s standards if I have published there before. (A1,E1)

Indeed, it seems that journal familiarity is connected closely to our confidence in reviewing, and while both authors ‘review for journals which I have published in and for those which I have not’ (A1,E1), A2 states that she is reluctant to ‘readily accept an offer to review for a journal that I’m not familiar with’, and A1 takes extra time to ‘do more preparatory work before I begin reading the manuscript and writing the review’ when reviewing for an unfamiliar journal.

Ecological systems

Microsystem.

Three microsystems exert influence on A1’s and A2’s development of feedback literacy: university, journal community, and Twitter.

In regards to the university, we are full-time academics in research-intensive universities in the UK and Japan where expectations for academics include publishing research in high-impact journals ‘which is vital to promotion’ (A1,E2). It is especially true in A2’s context where the national higher education agenda is to increase world rankings of universities. Thus, ‘there is little value placed on peer review, as it is not directly related to the broader agenda’ (A2,E2). When considering his recent relocation to the UK together with the current pandemic, A1 navigated his responsibilities within the university context and decided to allocate more time to his university-related responsibilities, especially providing learning and pastoral support to his students, who are mostly international students. Besides, A2 observed that there is a dearth of institution-wide support on conducting peer review although ‘there are a lot of training opportunities related to how to write academic papers in English, how to present at international conferences, how to write grant applications’, etc. (A2,E2). As a result, she ‘struggled for a couple of years’ because of the lack of institutional support for her development as a peer reviewer’ (A2,D2); but this helplessness also motivated her to seek her own ways to learn how to give feedback, such as ‘seeing through glimpses of other reviews, how others approach it, in terms of length, structure, tone, foci etc.’ (A2,E2). A1 shares the same view that no training is available at his institution to support his development as a peer reviewer. However, his postgraduate supervision experiences enabled him to reflect on how his feedback can benefit researchers. In our second online discussion, A1 shared that he held individual advising sessions with some postgraduate students, which made him realise that it is important for feedback to serve the function to inspire rather than to ‘give them right answers’ (A1,D2).

Because of the lack of formal training provided by universities, both authors searched for other professional communities to help us develop our expertise in giving feedback as peer reviewers, with journal communities being the next microsystem. We found that international journals provide valuable opportunities for us to understand more about the whole peer-review process, in particular the role of feedback. For A1, the training which he received from the editor-in-chief when he took up the associate editorship of a language education journal two years ago was particularly useful. A1 benefited greatly from meetings with the editor who walked him through every stage in the review process and provided ‘hands-on experience on how to handle delicate scenarios’ (A1,E2). Since then, A1 has had plenty of opportunities to oversee various stages of peer review and read a large number of reviewers’ reports which helped him gain ‘a holistic understanding of the peer-review process’ (A1,E2) and gradually made him become more cognizant of how he wants to give feedback. Although there was no explicit instruction on the technical aspect of giving feedback, A1 found that being an associate editor has developed his ‘consciousness’ and ‘awareness’ of giving feedback as a peer reviewer (A1,D2). Further, he felt that his editorial experiences provided him the awareness to constantly refine and improve his ways of giving feedback, especially ways to make his feedback ‘more structured, evidence-based, and objective’ (A1,E2). Despite not reflecting from the perspective of an editor, A2 recalled her experience as an author who received in-depth and constructive feedback from a reviewer, which really impacted the way she viewed the whole review process. She understood from this experience that even though the paper under review may not be particularly strong, peer reviewers should always aim to provide formative feedback which helps the authors to improve their work. These positive experiences of the two authors are impactful on the ways they give feedback as peer reviewers. In addition, close engagement with a specific journal has helped A2 to develop a sense of belonging, making it ‘much more than a journal, but also a way to become part of an academic community’ (A2,E2). With such a sense of belonging, it is more likely for her to be ‘pulled towards that journal than others’ when she can only review a limited number of manuscripts (A2,D2).

Another professional community in which we are both involved is Twitter. We regard Twitter as a platform for self-learning, reflection, and inspiration. We perceive Twitter as a space where we get to learn from others’ peer-review experiences and disciplinary practices. For example, A1 found the tweets on peer-review informative ‘because they are written by different stakeholders in the process—the authors, editors, reviewers’ and offer ‘different perspectives and sometimes different versions of the same story’ (A1,E2). A2 recalled a tweet she came across about the ‘infamous Reviewer 2’ and how she learned to not make the same mistakes (A2,D2). Reading other people’s experiences helps us reconsider our own feedback practices and, more broadly, the whole peer-review system because we ‘get a glimpse of the do’s and don’ts for peer reviewers’ (A1,E2).

Further to our three common microsystems, A2 also draws on a unique microsystem, that of her former profession as a teacher, which shapes her feedback practices in three ways. First, in her four years of teacher training, a lot of emphasis was placed on assessment and feedback such as ‘error correction’; this understanding related to giving feedback to students and was solidified through ‘learning on the job’ (A2,D2). Second, A2 acknowledges that as a teacher, she has a passion to ‘guide others in their knowledge and skill development… and continue this in our review practices’ (A2,E2). Finally, her teaching experience prepared her to consider the authors’ emotional responses in her peer-review feedback practices, constantly ‘thinking there’s a person there who’s going to be shattered getting a rejection’ (A2,D2).

Mesosystem considers the confluence of our interactions in various microsystems. Particularly, we experienced a lack of support from our institutions, which pushed us to seek alternative paths to acquire the art of giving feedback. This has made us realise the importance of self-learning in developing feedback literacy as peer reviewers, especially in how to develop constructive and actionable feedback. Both authors self-learn how to give feedback by reading others’ feedback. A1 felt ‘fortunate to be involved in journal editing and Twitter’ because he gets ‘a glimpse of how other peer reviewers give feedback to authors’ (A1,E2). A2, on the other hand, learned through her correspondences with a journal editor who made her stop ‘looking for every word’ and move away from ‘over proofreading and over editing’ (A2,D2).

Focusing on the chronosystem, it is noticed that both authors adjusted how they give feedback over time because of the aggregated influence of their microsystems. What stands out is that they have become more strategic in giving feedback. One way this is achieved is through focusing their comments on the arguments of the manuscripts instead of burning the midnight oil with error-correcting.

Exosystem concerns the environment where the focal individuals do not have direct interactions with the people in it but have access to information about. In his case, A1’s understanding of advising techniques promoted by a self-access language learning centre is conducive to the cultivation of his feedback literacy. Although A1 is not a part of the language advising team, he has a working relationship with the director. A1 was especially impressed by the learner-centeredness of an advising process:

The primary duty of the language advisor is not to be confused with that of a language teacher. Language teachers may teach a lecture on a linguistic feature or correct errors on an essay, but language advisors focus on designing activities and engaging students in dialogues to help them reflect on their own learning needs… The advisors may also suggest useful resources to the students which cater to their needs. In short, language advisors work in partnership with the students to help them improve their language while language teachers are often perceived as more authoritative figures (A1, E2).

His understanding of advising has affected how A1 provides feedback as a peer reviewer in a number of ways. First, A1 places much more emphasis on humanising his feedback, for example, by considering ‘ways to work in partnership with the authors and making this “partnership mindset” explicit to the authors through writing’ (A1,E2). One way to operationalise this ‘partnership mindset’ in peer review is to ‘ask a lot of questions’ and provide ‘multiple suggestions’ for the authors to choose from (A1,E2). Furthermore, his knowledge of the difference between feedback as giving advice and feedback as instruction has led him to include feedback, which points authors to additional resources. Below is a feedback point A1 gave in one of his reviews:

The description of the data analysis process was very brief. While we are not aiming at validity and reliability in qualitative studies, it is important for qualitative researchers to describe in detail how the data collected were analysed (e.g. iterative coding, inductive/deductive coding, thematic analysis) in order to ascertain that the findings were credible and trustworthy. See Johnny Saldaña’s ‘The Coding Manual for Qualitative Researchers’.

Another exosystem that we have knowledge about is formal peer-review training courses provided by publishers. These online courses are usually run asynchronously. Even though we did not enrol in these courses, our interest in peer review has led us to skim the content of these courses. Both of us questioned the value of formal peer-review training in developing feedback literacy of peer reviewers. For example, A2 felt that opportunities to review are more important because they ‘put you in that position where you have responsibility and have to think critically about how you are going to respond’ (A2,D2). To A1, formal peer-review training mostly focuses on developing peer reviewers’ ‘understanding of the whole mechanism’ but not providing ‘training on how to give feedback… For example, do you always ask a question without giving the answers you know? What is a good suggestion?’ (A1,D2).

Macrosystem

The two authors have diverse sociocultural experiences because of their family backgrounds and work contexts. When reflecting on their sociocultural experiences, A1 focused on his upbringing in Hong Kong where both of his parents are school teachers and his professional experience as a language teacher in secondary and tertiary education in Hong Kong while A2 discussed her experience of working in academia in Japan as an anglophone.

Observing his parents’ interactions with their students in schools, A1 was immersed in an Asian educational discourse characterised by ‘mutual respect and all sorts of formality’ (A1,E2). After he finished university, A1 became a school teacher and then a university lecturer (equivalent to a teaching fellow in the UK), getting immersed continuously in the etiquette of educational discourse in Hong Kong. Because of this, A1 knows that being professional means to be ‘formal and objective’ and there is a constant expectation to ‘treat people with respect’ (A1,E2). At the same time, his parents are unlike typical Asian parents; they are ‘more open-minded’, which made him more willing to listen and ‘consider different perspectives’ (A1,D2). Additionally, social hierarchy also impacted his approach to giving feedback as a peer reviewer. A1 started his career as a school teacher and then a university lecturer in Hong Kong with no formal research training. After obtaining his BA and MA, it is not until recently that A1 obtained his PhD by Prior Publication. Perhaps because of his background as a frontline teacher, A1 did not regard himself as ‘a formally trained researcher’ and perceived himself as not ‘elite enough to give feedback to other researchers’ (A1,E2). Both his childhood and his self-perceived identity have led to the formation of two feedback strategies: asking questions and providing a structured report mimicking the sections in the manuscript. A1 frequently asks questions in his reports ‘in a bid to offset some of the responsibilities to the authors’ (A1,E2). A1 struggles to decide whether to address authors using second- or third-person pronouns. A1 consistently uses third-person pronouns in his feedback because he wants to sound ‘very formal’ (A1,D2). However, A1 shared that he has recently started using second-person pronouns to make his feedback more interactive.

A2, on the other hand, pondered upon her sociocultural experiences as a school teacher in Australia, her position as an anglophone in a Japanese university, and her status as first-generation high school graduate. Reflecting on her career as a school teacher, A2 shared that her students had high expectations on her feedback:

So if you give feedback that seems unfair, you know … they’ll turn around and say, ‘What are you talking about’? They’re going to react back if your feedback is not clear. I think a lot of them [the students] appreciate the honesty. (A2,D2)

A2 acknowledges that her identity as a native English speaker has given her the advantage to publish extensively in international journals because of her high level of English proficiency and her access to ‘data from the US and from Australia which are more marketable’ (A2,D2). At the same time, as a native English speaker, she has empathy for her Japanese colleagues who struggle to write proficiently in English and some who even ‘pay thousands of dollars to have their work translated’ (A2,D2). Therefore, when giving feedback as a peer reviewer, she tries not to make a judgement on an author’s English proficiency and will not reject a paper based on the standard of English alone. Finally, as a first-generation scholar without any previous connections to academia, she struggles with belonging and self-confidence. As a result she notes that it usually takes her a long time to complete a review because she would like to be sure what she is saying is ‘right or constructive and is not on the wrong track’ (A2,D2).

Implications and future directions

In investigating the manifestations of the authors’ feedback literacy development, and the ecological systems in which this development occurs, this study unpacks the various sources of influence behind our feedback behaviours as two relatively new but highly commended peer reviewers. The findings show that our feedback literacy development is highly personalised and contextualised, and the sources of influence are diverse and interconnected, albeit largely informal. Our peer-review practices are influenced by our experiences within academia, but influences are much broader and begin much earlier. Peer-review skills were enhanced through direct experience not only in peer review but also in other activities related to the peer-review process, and as such more hands-on, on-site feedback training for peer reviewers may be more appropriate than knowledge-based training. The authors gain valuable insights from seeing the reviews of others, and as this is often not possible until scholars take on more senior roles within journals, co-reviewing is a potential way for ECRs to gain experience (McDowell et al., 2019 ). We draw practical and moral support from various communities, particularly online to promote “intellectual candour”, which refers to honest expressions of vulnerability for learning and trust building (Molloy and Bearman, 2019 , p. 32); in response to this finding we have developed an online community of practice, specifically as a space for discussing issues related to peer review (a Twitter account called “Scholarly Peers”). Importantly, our review practices are a product not only of how we review, but why we review, and as such training should not focus solely on the mechanics of review, but extend to its role within academia, and its impact not only on the quality of scholarship, but on the growth of researchers.

The significance of this study is its insider perspective, and the multifaceted framework that allows the capturing of the complexity of factors that influence individual feedback literacy development of two recognised peer reviewers. It must be stressed that the findings of this study are highly idiosyncratic, focusing on the experiences of only two peer reviewers and the educational research discipline. While the research design is such that it is not an attempt to describe a ‘typical’ or ‘expected’ experience, the scope of the study is a limitation, and future research could be expanded to studies of larger cohorts in order to identify broader trends. In this study, we have not included the reviewer reports themselves, and these reports provide a potentially rich source of data, which will be a focus in our continued investigation in this area. Further research could also investigate the role that peer-review training courses play in the feedback literacy development and practices of new and experienced peer reviewers. Since journal peer review is a communication process, it is equally important to investigate authors’ perspectives and experiences, especially pertaining to how authors interpret reviewers’ feedback based on the ways that it is written.

Data availability

Because of the sensitive nature of the data these are not made available.

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26 november 2021.

A Correction to this paper has been published: https://doi.org/10.1057/s41599-021-00996-3

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Chong, S.W., Mason, S. Demystifying the process of scholarly peer-review: an autoethnographic investigation of feedback literacy of two award-winning peer reviewers. Humanit Soc Sci Commun 8 , 266 (2021). https://doi.org/10.1057/s41599-021-00951-2

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Peer review is the independent assessment of your research paper by experts in your field. The purpose of peer review is to evaluate the paper’s quality and suitability for publication.

As well as peer review acting as a form of quality control for academic journals, it is a very useful source of feedback for you. The feedback can be used to improve your paper before it is published.

So at its best, peer review is a collaborative process, where authors engage in a dialogue with peers in their field, and receive constructive support to advance their work.

Use our free guide to discover how you can get the most out of the peer review process.

Why is peer review important?

Peer review is vitally important to uphold the high standards of scholarly communications, and maintain the quality of individual journals. It is also an important support for the researchers who author the papers.

Every journal depends on the hard work of reviewers who are the ones at the forefront of the peer review process. The reviewers are the ones who test and refine each article before publication. Even for very specialist journals, the editor can’t be an expert in the topic of every article submitted. So, the feedback and comments of carefully selected reviewers are an essential guide to inform the editor’s decision on a research paper.

There are also practical reasons why peer review is beneficial to you, the author. The peer review process can alert you to any errors in your work, or gaps in the literature you may have overlooked.

Researchers consistently tell us that their final published article is better than the version they submitted before peer review. 91% of respondents to a  Sense about Science peer review survey  said that their last paper was improved through peer review. A  Taylor & Francis study  supports this, finding that most researchers, across all subject areas, rated the contribution of peer review towards improving their article as 8 or above out of 10.

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Choose the right journal for your research: Think. Check. Submit

We support Think. Check. Submit. , an initiative launched by a coalition of scholarly communications organizations. It provides the tools to help you choose the right journal for your work.

Think. Check. Submit. was established because there are some journals which do not provide the quality assurance and services that should be delivered by a reputable journal. In particular, many of these journals do not make sure there is thorough peer review or editor feedback process in place.

That means, if you submit to one of these journals, you will not benefit from helpful article feedback from your peers. It may also lead to others being skeptical about the validity of your published results.

You should therefore make sure that you submit your work to a journal you can trust. By using the checklist provided on the Think. Check. Submit. website , you can make an informed choice.

Peer review integrity at Taylor & Francis

Every full research article published in a Taylor & Francis journal has been through peer review, as outlined in the journal’s aims & scope information. This means that the article’s quality, validity, and relevance has been assessed by independent peers within the research field.

We believe in the integrity of peer review with every journal we publish, ascribing to the following statement:

All published research articles in this journal have undergone rigorous peer review, based on initial editor screening, anonymous refereeing by independent expert referees, and consequent revision by article authors when required.

Different types of peer review

Peer review takes different forms and each type has pros and cons. The type of peer review model used will often vary between journals, even of the same publisher. So, check your chosen journal’s peer-review policy before you submit , to make sure you know what to expect and are comfortable with your paper being reviewed in that way.

Every Taylor & Francis journal publishes a statement describing the type of peer review used by the journal within the aims & scope section on Taylor & Francis Online.

Below we go through the most common types of peer review.

Common types of peer review

Single-anonymous peer review.

This type of peer review is also called ‘single-blind review’. In this model, the reviewers know that you are the author of the article, but you don’t know the identities of the reviewers.

Single-anonymous review is most common for science and medicine journals.

Find out more about the pros and cons of  single-anonymous peer review .

Double-anonymous peer review

In this model, which is also known as ‘double-blind review’, the reviewers don’t know that you are the author of the article. And you don’t know who the reviewers are either. Double-anonymous review is particularly common in humanities and some social sciences’ journals.

Discover more about the pros and cons of  double-anonymous peer review .

If you are submitting your article for double-anonymous peer review, make sure you know  how to make your article anonymous .

Open peer review

There is no one agreed definition of open peer review. In fact,  a recent study  identified 122 different definitions of the term. Typically, it will mean that the reviewers know you are the author and also that their identity will be revealed to you at some point during the review or publication process.

Find out more about  open peer review .

Post-publication peer review

In post-publication peer review models, your paper may still go through one of the other types of peer review first. Alternatively, your paper may be published online almost immediately, after some basic checks. Either way, once it is published, there will then be an opportunity for invited reviewers (or even readers) to add their own comments or reviews.

You can learn about the pros and cons of  post-publication peer review here.

Registered Reports

The  Registered Reports  process splits peer review into two parts.

The first round of peer review takes place after you’ve designed your study, but before you’ve collected or analyzed any data. This allows you to get feedback on both the question you’re looking to answer, and the experiment you’ve designed to test it.

If your manuscript passes peer review, the journal will give you an in-principle acceptance (IPA). This indicates that your article will be published as long as you successfully complete your study according to the pre-registered methods and submit an evidence-based interpretation of the results.

Explore Registered Reports at Taylor & Francis .

F1000 Research: Open and post-publication peer review

F1000Research  is part of the Taylor & Francis Group. It operates an innovative peer review process which is fully transparent and takes place after an article has been published.

How it works

Before publication, authors are asked to  suggest at least five potential reviewers  who are experts in the field. The reviewers also need to be able to provide unbiased reports on the article.

Submitted articles are published rapidly, after passing a series of pre-publication checks that assess, originality, readability, author eligibility, and compliance with F1000Research’s policies and ethical guidelines.

Once the article is published, expert reviewers are formally invited to review.

The peer review process is entirely open and transparent. Each peer review report, plus the approval status selected by the reviewer, is published with the reviewer’s name and affiliation alongside the article.

Authors are encouraged to respond openly to the peer review reports and can publish revised versions of their article if they wish. New versions are clearly linked and easily navigable, so that readers and reviewers can quickly find the latest version of an article.

The article remains published regardless of the reviewers’ reports. Articles that pass peer review are indexed in Scopus, PubMed, Google Scholar and other bibliographic databases.

How our publishing process works for articles

1. Article submission

Submitting an article is easy with our single-page submission system.

The in-house editorial team carries out a basic check on each submission to ensure that all policies are adhered to.

2. Publication and data deposition

Once the authors have analysed the manuscript, the article (with its associated source data) is published within a week, enabling immediate viewing and caution.

3. Open peer review & user commenting

Expert reviewers are selected and invited. Their reports and names are published alongside the article, together with the authors’ responses and comments from registered users.

4. Article revision

Authors are encouraged to publish revised versions of their article. All versions of an article are linked and independently citable.

Articles that pass peer review are indexed in external databases such as PubMed, Scopus and Google Scholar.

Discover more about how the F1000Research model works .

Get to know the peer review process

Peer review follows a number of steps, beginning with submitting your article to a journal.

Step 1: Editor assessment

When your manuscript arrives at the journal’s editorial office it will receive an initial desk assessment by the journal’s editor or editorial office. They will check that it’s broadly suitable for the journal.

They will ask questions such as:

Is this the right journal for this article?

Does the paper cover a suitable topic according to the journal’s  aims & scope ?

Has the author followed the journal’s guidelines in the  instructions for authors ? They will check that your paper meets the basic requirements of the journal, such as word count, language clarity, and format.

Has the author included everything that’s needed for peer review? They will check that there is an abstract, author affiliation details, any figures, and research-funder information.

Does it make a significant contribution to the existing literature?

If your article doesn’t pass these initial checks the editor might reject the article immediately. This is known as a ‘desk reject’ and it is a decision made at the editor’s discretion, based on their substantial experience and subject expertise. By having this initial screening in place, it can enable a quick decision if your manuscript isn’t suitable for the journal. This means you can submit your article to another journal quickly.

If your article does pass the initial assessment, it will move to the next stage, and into peer review.

“As an editor, when you first get a submission, at one level you’re simply filtering. A fairly small proportion do not get sent out by me for review. Sometimes they simply fall outside the scope of the journal.”

– Michael Reiss, Founding Editor of Sex Education

Step 2: First round of peer review

Next, the editor will find and contact other researchers who are experts in your field, and will ask them to review the paper. A minimum of two independent reviewers is normally required for every research article. The aims and scope of each journal will outline their peer review policy in detail.

The reviewers will be asked to read and comment on your article. They may also be invited to advise the editor whether your article is suitable for publication in that journal.

So, what are the reviewers looking for?

This depends on the subject area, but they will be checking that:

Your work is original or new.

The study design and methodology are appropriate and described so that others could replicate what you have done.

You’ve engaged with all the relevant current scholarship.

The results are appropriately and clearly presented.

Your conclusions are reliable, significant, and supported by the research.

The paper fits the scope of the journal.

The work is of a high enough standard to be published in the journal.

If you have not already  shared your research data publicly , peer reviewers may request to see your datasets, to support validation of the results in your article.

Once the editor has received and considered the reviewer reports, as well as making their own assessment of your work, they will let you know their decision. The reviewer reports will be shared with you, along with any additional guidance from the editor.

If you get a straight acceptance, congratulations, your article is ready to move to publication. But, please note, that this isn’t common. Very often, you will need to revise your article and resubmit it. Or it may be that the editor decides your paper needs to be rejected by that journal.

Please note that the final editorial decision on a paper and the choice of who to invite to review is always the editor’s decision. For further details on this, please see  our peer review appeals and complaints policy.

Step 3: Revise and resubmit

It is very common for the editor and reviewers to have suggestions about how you can improve your paper before it is ready to be published. They might have only a few straightforward recommendations (‘minor amendments’) or require more substantial changes before your paper will be accepted for publication (‘major amendments’). Authors often tell us that the reviewers’ comments can be extremely helpful, to make sure that their article is of a high quality.

During this stage of the process you will have time to amend your article based on the reviewers’ comments, resubmitting it with any or all changes made. Make sure you know how to respond to reviewer comments, we cover this in the next section.

Once you resubmit your manuscript the editor will look through the revisions. They will often send it out for a second round of peer review, asking the reviewers to assess how you’ve responded to their comments.

After this, you may be asked to make further revisions, or the paper might be rejected if the editor thinks that the changes you’ve made are not adequate. However, if your revisions have now brought the paper up to the standard required by that journal, it then moves to the next stage.

If you do not intend to make the revisions suggested by the journal and resubmit your paper for consideration, please make sure you formally withdraw your paper from consideration by the journal before you submit elsewhere.

Make sure you resubmit

If you have not already shared your research data publicly , peer reviewers may request to see your datasets to support the validation of the results in your article.

Step 4: Accepted

And that’s it, you’ve made it through peer review. The next step is  production

How long does peer review take?

Editorial teams work very hard to progress papers through peer review as quickly as possible. But it is important to be aware that this part of the process can take time.

The first stage is for the editor to find suitably qualified expert reviewers who are available. Given the competing demands of research life, nobody can agree to every review request they receive. It’s therefore not uncommon for a paper to go through several cycles of requests before the editor finds reviewers who are both willing and able to accept.

Then, the reviewers who do accept the request, have to find time alongside their own research, teaching, and writing, to give your paper thorough consideration.

Please do keep this in mind if you don’t receive a decision on your paper as quickly as you would like. If you’ve submitted your paper via an online system, you can use it to track the progress of your paper through peer review. Otherwise, if you need an update on the status of your paper, please get in touch with the editor.

Many journals publish key dates alongside new articles, including when the paper was submitted, accepted, and published online. While you’re at the stage of choosing a journal to submit to, take a look at these dates for a range of recent articles published in the journals you’re considering. While each article will have a slightly different timeline, this may help you to get an idea of how long publication may take.

A 360⁰ view of peer review

Peer review is a process that involves various players – the author, the reviewer and the editor to name a few. And depending on which of these hats you have on, the process can look quite different.

To help you uncover the 360⁰ peer review view,  read these interviews  with an editor, author, and reviewer.

How to respond to reviewer comments

If the editor asks you to revise your article, you will be given time to make the required changes before resubmitting.

When you receive the reviewers’ comments, try not to take personal offence to any criticism of your article (even though that can be hard).

Some researchers find it helpful to put the reviewer report to one side for a few days after they’ve read it for the first time. Once you have had chance to digest the idea that your article requires further work, you can more easily address the reviewer comments objectively.

When you come back to the reviewer report, take time to read through the editor and reviewers’ advice carefully, deciding what changes you will make to your article in response. Taking their points on board will make sure your final article is as robust and impactful as possible.

Please make sure that you address all the reviewer and editor comments in your revisions.

It may be helpful to resubmit your article along with a two-column grid outlining how you’ve revised your manuscript. On one side of the grid list each of the reviewers’ comments and opposite them detail the alterations you’ve made in response. This method can help you to order your thoughts, and clearly demonstrate to the editor and reviewers that you’ve considered all of their feedback.

If there are any review comments which you don’t understand or don’t know how to respond to, please get in touch with the journal’s editor and ask for their advice.

What if you don’t agree with the reviewers’ comments?

If there’s a review comment that you don’t agree with, it is important that you don’t ignore it. Instead, include an explanation of why you haven’t made that change with your resubmission. The editor can then make an assessment and include your explanation when the amended article is sent back to the reviewers.

You are entitled to defend your position but, when you do, make sure that the tone of your explanation is assertive and persuasive, rather than defensive or aggressive.

“Where possible, a little constructive advice on how to make use of the views of the referees can make all the difference, and the editor has the responsibility of deciding when and how to do this.”

– Gary McCulloch, Editor, British Journal of Educational Studies

What if my paper is rejected?

Nobody enjoys having their paper rejected by a journal, but it is a fact of academic life. It happens to almost all researchers at some point in their career. So, it is important not to let the experience knock you back. Instead, try to use it as a valuable learning opportunity.

Take time to understand why your paper has been rejected

If a journal rejects your manuscript, it may be for one of many reasons. Make sure that you understand why your paper has been rejected so that you can learn from the experience. This is especially important if you are intending to submit the same article to a different journal.

Are there fundamental changes that need to be made before the paper is ready to be published, or was this simply a case of submitting to the wrong journal? If you are unsure why your article has been rejected, then please contact the journal’s editor for advice.

Some of the common reasons manuscripts are rejected

The author has submitted their paper to the wrong journal: it doesn’t fit the  aims & scope  or fails to engage with issues addressed by the journal.

The manuscript is not a true journal article, for instance it is too journalistic or clearly a thesis chapter.

The manuscript is too long or too short.

There is poor regard of the journal’s conventions, or for academic writing in general.

Poor style, grammar, punctuation or English throughout the manuscript. Get  English language editing  assistance.

The manuscript does not make any new contribution to the subject.

The research has not been properly contextualized.

There is a poor theoretical framework used. There are  actio nable recommendations to improve your manuscript .

The manuscript is poorly presented.

The manuscript is libelous or unethical.

Carefully consider where to submit next

When you made your original submission, you will probably have had a shortlist of journals you were considering. Return to that list but, before you move to your second choice, you may wish to assess whether any feedback you’ve received during peer review has changed your opinion. Your article may also be quite different if it has been through any rounds of revision. It can be helpful at this stage to re-read the  aims & scope  statements of your original shortlisted journals.

Once you have selected which journal to submit to next, make sure that you read through its information for authors and reformat your article to fit its requirements. Again, it is important to use the feedback from the peer review process to your advantage as you rewrite and reformat the manuscript.

Is ‘transferring’ an option?

A growing number of publishers offer a  transfer or cascade service  to authors when their paper is rejected. This process is designed for papers which aren’t suitable for the journal they were originally submitted to.

If your article falls into this category then one or more alternative journals from the same publisher will be suggested. You will have the option either to submit to one of those suggested journals for review or to withdraw your article.

If you choose to transfer your article this will usually save you time. You won’t need to enter all of the details into a new submission system. Once you’ve made any changes to your paper, bearing in mind previous editor or reviewer comments, the article will be submitted to the new journal on your behalf.

We have some more information about  article transfers, and also some FAQs about the Taylor & Francis transfer process.

Why you should become a peer reviewer

When you’re not in the middle of submitting or revising your own article, you should consider becoming a reviewer yourself.

There are many demands on a researcher’s time, so it is a legitimate question to ask why some of that precious time should be spent reviewing someone else’s work. How does being a reviewer help you in your career? Here are some of the benefits.

Keep up with the latest thinking As a reviewer you get an early view of the exciting new research being done in your field. Not only that, peer review gives you a role in helping to evaluate and improve this new work.

Improve your own writing Carefully reviewing articles written by other researchers can give you an insight into how you can make your own work better. Unlike when you are reading articles as part of your research, the process of reviewing encourages you to think critically about what makes an article good (or not so good). This could be related to writing style, presentation, or the clarity of explanations.

Boost your career While a lot of reviewing is anonymous, there are schemes to recognize the important contribution of reviewers. You can also include reviewing work on your resume. Your work as a reviewer will be of interest to appointment or promotion committees who are looking for evidence of service to the profession.

Become part of a journal’s community Many journals act as the center of a network of researchers who are in conversation about key themes and developments in the field. Becoming a reviewer is a great way to get involved with that group. This can give you the opportunity to build new connections for future collaborations. Being a regular reviewer may also be the first step to becoming a member of the journal’s editorial board.

Your research community needs you

Of course, being a reviewer is not just about the benefits it can bring you. The  Taylor & Francis peer review survey  found that these are the top 3 reasons why researchers choose to review:

Being an active member of the academic community Peer review is the bedrock of academic publishing. The work of reviewers is essential in helping every piece of research to become as good as it can be. By being a reviewer, you will play a vital part in advancing the research area that you care about.

Reciprocating the benefit Researchers regularly talk about the benefits to their own work from being reviewed by others. Gratitude to the reviewers who have improved your work is a great motivation to make one’s own contribution of service to the community.

Enjoying being able to help improve papers Reviewing is often anonymous, with only the editor knowing the important contribution you’ve made. However, many reviewers attest that it is work that makes them feel good, knowing that they have been able to support a fellow researcher.

How to be an effective peer reviewer

Our popular  guide to becoming a peer reviewer  covers everything you need to know to get started, including:

How to become a peer reviewer

Writing review reports: step-by-step

Ethical guidelines for peer reviewers

Reviewer recognition

Read the  Taylor & Francis reviewer guidelines .

“Reviewers are the lifeblood of any journal”

– Mike J. Smith, Editor-in-Chief of Journal of Maps

Further reading

We hope you’ve found this short introduction to peer review helpful. For further useful advice check out the following resources.

Further resources

Peer Review: the nuts and bolts A guide to peer review written by early career researchers, for early career researchers and published by Sense about Science.

A guide to becoming a peer reviewer An overview of what’s involved in becoming a reviewer for a Taylor & Francis journal.

Ethical guidelines for peer reviewer Produced by COPE, the Committee on Publication Ethics, setting out the standards all peer reviewers should follow.

Using peer review effectively: quick tips Advice available to staff and students at institutions with a Vitae membership.

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What is peer review?

Reviewers play a pivotal role in scholarly publishing. The peer review system exists to validate academic work, helps to improve the quality of published research, and increases networking possibilities within research communities. Despite criticisms, peer review is still the only widely accepted method for research validation and has continued successfully with relatively minor changes for some 350 years.

Elsevier relies on the peer review process to uphold the quality and validity of individual articles and the journals that publish them.

Peer review has been a formal part of scientific communication since the first scientific journals appeared more than 300 years ago. The Philosophical Transactions   opens in new tab/window of the Royal Society is thought to be the first journal to formalize the peer review process   opens in new tab/window under the editorship of Henry Oldenburg (1618- 1677).

Despite many criticisms about the integrity of peer review, the majority of the research community still believes peer review is the best form of scientific evaluation. This opinion was endorsed by the outcome of a survey Elsevier and Sense About Science conducted in 2009   opens in new tab/window and has since been further confirmed by other publisher and scholarly organization surveys. Furthermore, a  2015 survey by the Publishing Research Consortium   opens in new tab/window , saw 82% of researchers agreeing that “without peer review there is no control in scientific communication.”

To learn more about peer review, visit Elsevier’s free e-learning platform  Researcher Academy   opens in new tab/window and see our resources below.

The peer review process

Types of peer review.

Peer review comes in different flavours. Each model has its own advantages and disadvantages, and often one type of review will be preferred by a subject community. Before submitting or reviewing a paper, you must therefore check which type is employed by the journal so you are aware of the respective rules. In case of questions regarding the peer review model employed by the journal for which you have been invited to review, consult the journal’s homepage or contact the editorial office directly.  

Single anonymized review

In this type of review, the names of the reviewers are hidden from the author. This is the traditional method of reviewing and is the most common type by far. Points to consider regarding single anonymized review include:

Reviewer anonymity allows for impartial decisions, as the reviewers will not be influenced by potential criticism from the authors.

Authors may be concerned that reviewers in their field could delay publication, giving the reviewers a chance to publish first.

Reviewers may use their anonymity as justification for being unnecessarily critical or harsh when commenting on the authors’ work.

Double anonymized review

Both the reviewer and the author are anonymous in this model. Some advantages of this model are listed below.

Author anonymity limits reviewer bias, such as on author's gender, country of origin, academic status, or previous publication history.

Articles written by prestigious or renowned authors are considered based on the content of their papers, rather than their reputation.

But bear in mind that despite the above, reviewers can often identify the author through their writing style, subject matter, or self-citation – it is exceedingly difficult to guarantee total author anonymity. More information for authors can be found in our  double-anonymized peer review guidelines .

Triple anonymized review

With triple anonymized review, reviewers are anonymous to the author, and the author's identity is unknown to both the reviewers and the editor. Articles are anonymized at the submission stage and are handled in a way to minimize any potential bias towards the authors. However, it should be noted that: 

The complexities involved with anonymizing articles/authors to this level are considerable.

As with double anonymized review, there is still a possibility for the editor and/or reviewers to correctly identify the author(s) from their writing style, subject matter, citation patterns, or other methodologies.

Open review

Open peer review is an umbrella term for many different models aiming at greater transparency during and after the peer review process. The most common definition of open review is when both the reviewer and author are known to each other during the peer review process. Other types of open peer review consist of:

Publication of reviewers’ names on the article page 

Publication of peer review reports alongside the article, either signed or anonymous 

Publication of peer review reports (signed or anonymous) with authors’ and editors’ responses alongside the article 

Publication of the paper after pre-checks and opening a discussion forum to the community who can then comment (named or anonymous) on the article 

Many believe this is the best way to prevent malicious comments, stop plagiarism, prevent reviewers from following their own agenda, and encourage open, honest reviewing. Others see open review as a less honest process, in which politeness or fear of retribution may cause a reviewer to withhold or tone down criticism. For three years, five Elsevier journals experimented with publication of peer review reports (signed or anonymous) as articles alongside the accepted paper on ScienceDirect ( example   opens in new tab/window ).

Read more about the experiment

More transparent peer review

Transparency is the key to trust in peer review and as such there is an increasing call towards more  transparency around the peer review process . In an effort to promote transparency in the peer review process, many Elsevier journals therefore publish the name of the handling editor of the published paper on ScienceDirect. Some journals also provide details about the number of reviewers who reviewed the article before acceptance. Furthermore, in order to provide updates and feedback to reviewers, most Elsevier journals inform reviewers about the editor’s decision and their peers’ recommendations. 

Article transfer service: sharing reviewer comments

Elsevier authors may be invited to  transfer  their article submission from one journal to another for free if their initial submission was not successful. 

As a referee, your review report (including all comments to the author and editor) will be transferred to the destination journal, along with the manuscript. The main benefit is that reviewers are not asked to review the same manuscript several times for different journals. 

Tools & resources

Elsevier researcher academy modules.

The certified peer reviewer course   opens in new tab/window

Transparency in peer review   opens in new tab/window

Reviewers’ Update articles

Peer review using today’s technology

Lifting the lid on publishing peer review reports: an interview with Bahar Mehmani and Flaminio Squazzoni

How face-to-face peer review can benefit authors and journals alike

Innovation in peer review: introducing “volunpeers”

Results masked review: peer review without publication bias

Interesting reads

"Is Peer Review in Crisis?" Perspectives in Publishing No 2, August 2004, by Adrian Mulligan   opens in new tab/window

“The history of the peer-review process” Trends in Biotechnology, 2002, by Ray Spier   opens in new tab/window

Publishing Research Consortium Peer review survey. 2015. Elsevier   opens in new tab/window

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Writing a Scientific Review Article: Comprehensive Insights for Beginners

Ayodeji amobonye.

1 Department of Biotechnology and Food Science, Faculty of Applied Sciences, Durban University of Technology, P.O. Box 1334, KwaZulu-Natal, Durban 4000, South Africa

2 Writing Centre, Durban University of Technology, P.O. Box 1334 KwaZulu-Natal, Durban 4000, South Africa

Japareng Lalung

3 School of Industrial Technology, Universiti Sains Malaysia, Gelugor 11800, Pulau Pinang, Malaysia

Santhosh Pillai

Associated data.

The data and materials that support the findings of this study are available from the corresponding author upon reasonable request.

Review articles present comprehensive overview of relevant literature on specific themes and synthesise the studies related to these themes, with the aim of strengthening the foundation of knowledge and facilitating theory development. The significance of review articles in science is immeasurable as both students and researchers rely on these articles as the starting point for their research. Interestingly, many postgraduate students are expected to write review articles for journal publications as a way of demonstrating their ability to contribute to new knowledge in their respective fields. However, there is no comprehensive instructional framework to guide them on how to analyse and synthesise the literature in their niches into publishable review articles. The dearth of ample guidance or explicit training results in students having to learn all by themselves, usually by trial and error, which often leads to high rejection rates from publishing houses. Therefore, this article seeks to identify these challenges from a beginner's perspective and strives to plug the identified gaps and discrepancies. Thus, the purpose of this paper is to serve as a systematic guide for emerging scientists and to summarise the most important information on how to write and structure a publishable review article.

1. Introduction

Early scientists, spanning from the Ancient Egyptian civilization to the Scientific Revolution of the 16 th /17 th century, based their research on intuitions, personal observations, and personal insights. Thus, less time was spent on background reading as there was not much literature to refer to. This is well illustrated in the case of Sir Isaac Newton's apple tree and the theory of gravity, as well as Gregor Mendel's pea plants and the theory of inheritance. However, with the astronomical expansion in scientific knowledge and the emergence of the information age in the last century, new ideas are now being built on previously published works, thus the periodic need to appraise the huge amount of already published literature [ 1 ]. According to Birkle et al. [ 2 ], the Web of Science—an authoritative database of research publications and citations—covered more than 80 million scholarly materials. Hence, a critical review of prior and relevant literature is indispensable for any research endeavour as it provides the necessary framework needed for synthesising new knowledge and for highlighting new insights and perspectives [ 3 ].

Review papers are generally considered secondary research publications that sum up already existing works on a particular research topic or question and relate them to the current status of the topic. This makes review articles distinctly different from scientific research papers. While the primary aim of the latter is to develop new arguments by reporting original research, the former is focused on summarising and synthesising previous ideas, studies, and arguments, without adding new experimental contributions. Review articles basically describe the content and quality of knowledge that are currently available, with a special focus on the significance of the previous works. To this end, a review article cannot simply reiterate a subject matter, but it must contribute to the field of knowledge by synthesising available materials and offering a scholarly critique of theory [ 4 ]. Typically, these articles critically analyse both quantitative and qualitative studies by scrutinising experimental results, the discussion of the experimental data, and in some instances, previous review articles to propose new working theories. Thus, a review article is more than a mere exhaustive compilation of all that has been published on a topic; it must be a balanced, informative, perspective, and unbiased compendium of previous studies which may also include contrasting findings, inconsistencies, and conventional and current views on the subject [ 5 ].

Hence, the essence of a review article is measured by what is achieved, what is discovered, and how information is communicated to the reader [ 6 ]. According to Steward [ 7 ], a good literature review should be analytical, critical, comprehensive, selective, relevant, synthetic, and fully referenced. On the other hand, a review article is considered to be inadequate if it is lacking in focus or outcome, overgeneralised, opinionated, unbalanced, and uncritical [ 7 ]. Most review papers fail to meet these standards and thus can be viewed as mere summaries of previous works in a particular field of study. In one of the few studies that assessed the quality of review articles, none of the 50 papers that were analysed met the predefined criteria for a good review [ 8 ]. However, beginners must also realise that there is no bad writing in the true sense; there is only writing in evolution and under refinement. Literally, every piece of writing can be improved upon, right from the first draft until the final published manuscript. Hence, a paper can only be referred to as bad and unfixable when the author is not open to corrections or when the writer gives up on it.

According to Peat et al. [ 9 ], “everything is easy when you know how,” a maxim which applies to scientific writing in general and review writing in particular. In this regard, the authors emphasized that the writer should be open to learning and should also follow established rules instead of following a blind trial-and-error approach. In contrast to the popular belief that review articles should only be written by experienced scientists and researchers, recent trends have shown that many early-career scientists, especially postgraduate students, are currently expected to write review articles during the course of their studies. However, these scholars have little or no access to formal training on how to analyse and synthesise the research literature in their respective fields [ 10 ]. Consequently, students seeking guidance on how to write or improve their literature reviews are less likely to find published works on the subject, particularly in the science fields. Although various publications have dealt with the challenges of searching for literature, or writing literature reviews for dissertation/thesis purposes, there is little or no information on how to write a comprehensive review article for publication. In addition to the paucity of published information to guide the potential author, the lack of understanding of what constitutes a review paper compounds their challenges. Thus, the purpose of this paper is to serve as a guide for writing review papers for journal publishing. This work draws on the experience of the authors to assist early-career scientists/researchers in the “hard skill” of authoring review articles. Even though there is no single path to writing scientifically, or to writing reviews in particular, this paper attempts to simplify the process by looking at this subject from a beginner's perspective. Hence, this paper highlights the differences between the types of review articles in the sciences while also explaining the needs and purpose of writing review articles. Furthermore, it presents details on how to search for the literature as well as how to structure the manuscript to produce logical and coherent outputs. It is hoped that this work will ease prospective scientific writers into the challenging but rewarding art of writing review articles.

2. Benefits of Review Articles to the Author

Analysing literature gives an overview of the “WHs”: WHat has been reported in a particular field or topic, WHo the key writers are, WHat are the prevailing theories and hypotheses, WHat questions are being asked (and answered), and WHat methods and methodologies are appropriate and useful [ 11 ]. For new or aspiring researchers in a particular field, it can be quite challenging to get a comprehensive overview of their respective fields, especially the historical trends and what has been studied previously. As such, the importance of review articles to knowledge appraisal and contribution cannot be overemphasised, which is reflected in the constant demand for such articles in the research community. However, it is also important for the author, especially the first-time author, to recognise the importance of his/her investing time and effort into writing a quality review article.

Generally, literature reviews are undertaken for many reasons, mainly for publication and for dissertation purposes. The major purpose of literature reviews is to provide direction and information for the improvement of scientific knowledge. They also form a significant component in the research process and in academic assessment [ 12 ]. There may be, however, a thin line between a dissertation literature review and a published review article, given that with some modifications, a literature review can be transformed into a legitimate and publishable scholarly document. According to Gülpınar and Güçlü [ 6 ], the basic motivation for writing a review article is to make a comprehensive synthesis of the most appropriate literature on a specific research inquiry or topic. Thus, conducting a literature review assists in demonstrating the author's knowledge about a particular field of study, which may include but not be limited to its history, theories, key variables, vocabulary, phenomena, and methodologies [ 10 ]. Furthermore, publishing reviews is beneficial as it permits the researchers to examine different questions and, as a result, enhances the depth and diversity of their scientific reasoning [ 1 ]. In addition, writing review articles allows researchers to share insights with the scientific community while identifying knowledge gaps to be addressed in future research. The review writing process can also be a useful tool in training early-career scientists in leadership, coordination, project management, and other important soft skills necessary for success in the research world [ 13 ]. Another important reason for authoring reviews is that such publications have been observed to be remarkably influential, extending the reach of an author in multiple folds of what can be achieved by primary research papers [ 1 ]. The trend in science is for authors to receive more citations from their review articles than from their original research articles. According to Miranda and Garcia-Carpintero [ 14 ], review articles are, on average, three times more frequently cited than original research articles; they also asserted that a 20% increase in review authorship could result in a 40–80% increase in citations of the author. As a result, writing reviews can significantly impact a researcher's citation output and serve as a valuable channel to reach a wider scientific audience. In addition, the references cited in a review article also provide the reader with an opportunity to dig deeper into the topic of interest. Thus, review articles can serve as a valuable repository for consultation, increasing the visibility of the authors and resulting in more citations.

3. Types of Review Articles

The first step in writing a good literature review is to decide on the particular type of review to be written; hence, it is important to distinguish and understand the various types of review articles. Although scientific review articles have been classified according to various schemes, however, they are broadly categorised into narrative reviews, systematic reviews, and meta-analyses [ 15 ]. It was observed that more authors—as well as publishers—were leaning towards systematic reviews and meta-analysis while downplaying narrative reviews; however, the three serve different aims and should all be considered equally important in science [ 1 ]. Bibliometric reviews and patent reviews, which are closely related to meta-analysis, have also gained significant attention recently. However, from another angle, a review could also be of two types. In the first class, authors could deal with a widely studied topic where there is already an accumulated body of knowledge that requires analysis and synthesis [ 3 ]. At the other end of the spectrum, the authors may have to address an emerging issue that would benefit from exposure to potential theoretical foundations; hence, their contribution would arise from the fresh theoretical foundations proposed in developing a conceptual model [ 3 ].

3.1. Narrative Reviews

Narrative reviewers are mainly focused on providing clarification and critical analysis on a particular topic or body of literature through interpretative synthesis, creativity, and expert judgement. According to Green et al. [ 16 ], a narrative review can be in the form of editorials, commentaries, and narrative overviews. However, editorials and commentaries are usually expert opinions; hence, a beginner is more likely to write a narrative overview, which is more general and is also referred to as an unsystematic narrative review. Similarly, the literature review section of most dissertations and empirical papers is typically narrative in nature. Typically, narrative reviews combine results from studies that may have different methodologies to address different questions or to formulate a broad theoretical formulation [ 1 ]. They are largely integrative as strong focus is placed on the assimilation and synthesis of various aspects in the review, which may involve comparing and contrasting research findings or deriving structured implications [ 17 ]. In addition, they are also qualitative studies because they do not follow strict selection processes; hence, choosing publications is relatively more subjective and unsystematic [ 18 ]. However, despite their popularity, there are concerns about their inherent subjectivity. In many instances, when the supporting data for narrative reviews are examined more closely, the evaluations provided by the author(s) become quite questionable [ 19 ]. Nevertheless, if the goal of the author is to formulate a new theory that connects diverse strands of research, a narrative method is most appropriate.

3.2. Systematic Reviews

In contrast to narrative reviews, which are generally descriptive, systematic reviews employ a systematic approach to summarise evidence on research questions. Hence, systematic reviews make use of precise and rigorous criteria to identify, evaluate, and subsequently synthesise all relevant literature on a particular topic [ 12 , 20 ]. As a result, systematic reviews are more likely to inspire research ideas by identifying knowledge gaps or inconsistencies, thus helping the researcher to clearly define the research hypotheses or questions [ 21 ]. Furthermore, systematic reviews may serve as independent research projects in their own right, as they follow a defined methodology to search and combine reliable results to synthesise a new database that can be used for a variety of purposes [ 22 ]. Typically, the peculiarities of the individual reviewer, different search engines, and information databases used all ensure that no two searches will yield the same systematic results even if the searches are conducted simultaneously and under identical criteria [ 11 ]. Hence, attempts are made at standardising the exercise via specific methods that would limit bias and chance effects, prevent duplications, and provide more accurate results upon which conclusions and decisions can be made.

The most established of these methods is the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines which objectively defined statements, guidelines, reporting checklists, and flowcharts for undertaking systematic reviews as well as meta-analysis [ 23 ]. Though mainly designed for research in medical sciences, the PRISMA approach has gained wide acceptance in other fields of science and is based on eight fundamental propositions. These include the explicit definition of the review question, an unambiguous outline of the study protocol, an objective and exhaustive systematic review of reputable literature, and an unambiguous identification of included literature based on defined selection criteria [ 24 ]. Other considerations include an unbiased appraisal of the quality of the selected studies (literature), organic synthesis of the evidence of the study, preparation of the manuscript based on the reporting guidelines, and periodic update of the review as new data emerge [ 24 ]. Other methods such as PRISMA-P (Preferred Reporting Items for Systematic review and Meta-Analysis Protocols), MOOSE (Meta-analysis Of Observational Studies in Epidemiology), and ROSES (Reporting Standards for Systematic Evidence Syntheses) have since been developed for systematic reviews (and meta-analysis), with most of them being derived from PRISMA.

Consequently, systematic reviews—unlike narrative reviews—must contain a methodology section which in addition to all that was highlighted above must fully describe the precise criteria used in formulating the research question and setting the inclusion or exclusion criteria used in selecting/accessing the literature. Similarly, the criteria for evaluating the quality of the literature included in the review as well as for analysing, synthesising, and disseminating the findings must be fully described in the methodology section.

3.3. Meta-Analysis

Meta-analyses are considered as more specialised forms of systematic reviews. Generally, they combine the results of many studies that use similar or closely related methods to address the same question or share a common quantitative evaluation method [ 25 ]. However, meta-analyses are also a step higher than other systematic reviews as they are focused on numerical data and involve the use of statistics in evaluating different studies and synthesising new knowledge. The major advantage of this type of review is the increased statistical power leading to more reliable results for inferring modest associations and a more comprehensive understanding of the true impact of a research study [ 26 ]. Unlike in traditional systematic reviews, research topics covered in meta-analyses must be mature enough to allow the inclusion of sufficient homogeneous empirical research in terms of subjects, interventions, and outcomes [ 27 , 28 ].

Being an advanced form of systematic review, meta-analyses must also have a distinct methodology section; hence, the standard procedures involved in the traditional systematic review (especially PRISMA) also apply in meta-analyses [ 23 ]. In addition to the common steps in formulating systematic reviews, meta-analyses are required to describe how nested and missing data are handled, the effect observed in each study, the confidence interval associated with each synthesised effect, and any potential for bias presented within the sample(s) [ 17 ]. According to Paul and Barari [ 28 ], a meta-analysis must also detail the final sample, the meta-analytic model, and the overall analysis, moderator analysis, and software employed. While the overall analysis involves the statistical characterization of the relationships between variables in the meta-analytic framework and their significance, the moderator analysis defines the different variables that may affect variations in the original studies [ 28 , 29 ]. It must also be noted that the accuracy and reliability of meta-analyses have both been significantly enhanced by the incorporation of statistical approaches such as Bayesian analysis [ 30 ], network analysis [ 31 ], and more recently, machine learning [ 32 ].

3.4. Bibliometric Review

A bibliometric review, commonly referred to as bibliometric analysis, is a systematic evaluation of published works within a specific field or discipline [ 33 ]. This bibliometric methodology involves the use of quantitative methods to analyse bibliometric data such as the characteristics and numbers of publications, units of citations, authorship, co-authorship, and journal impact factors [ 34 ]. Academics use bibliometric analysis with different objectives in mind, which includes uncovering emerging trends in article and journal performance, elaborating collaboration patterns and research constituents, evaluating the impact and influence of particular authors, publications, or research groups, and highlighting the intellectual framework of a certain field [ 35 ]. It is also used to inform policy and decision-making. Similarly to meta-analysis, bibliometric reviews rely upon quantitative techniques, thus avoiding the interpretation bias that could arise from the qualitative techniques of other types of reviews [ 36 ]. However, while bibliometric analysis synthesises the bibliometric and intellectual structure of a field by examining the social and structural linkages between various research parts, meta-analysis focuses on summarising empirical evidence by probing the direction and strength of effects and relationships among variables, especially in open research questions [ 37 , 38 ]. However, similarly to systematic review and meta-analysis, a bibliometric review also requires a well-detailed methodology section. The amount of data to be analysed in bibliometric analysis is quite massive, running to hundreds and tens of thousands in some cases. Although the data are objective in nature (e.g., number of citations and publications and occurrences of keywords and topics), the interpretation is usually carried out through both objective (e.g., performance analysis) and subjective (e.g., thematic analysis) evaluations [ 35 ]. However, the invention and availability of bibliometric software such as BibExcel, Gephi, Leximancer, and VOSviewer and scientific databases such as Dimensions, Web of Science, and Scopus have made this type of analysis more feasible.

3.5. Patent Review

Patent reviews provide a comprehensive analysis and critique of a specific patent or a group of related patents, thus presenting a concise understanding of the technology or innovation that is covered by the patent [ 39 ]. This type of article is useful for researchers as it also enhances their understanding of the legal, technical, and commercial aspects of an intellectual property/innovation; in addition, it is also important for stakeholders outside the research community including IP (intellectual property) specialists, legal professionals, and technology-transfer officers [ 40 ]. Typically, patent reviews encompass the scope, background, claims, legal implications, technical specifications, and potential commercial applications of the patent(s). The article may also include a discussion of the patent's strengths and weaknesses, as well as its potential impact on the industry or field in which it operates. Most times, reviews are time specified, they may be regionalised, and the data are usually retrieved via patent searches on databases such as that of the European Patent Office ( https://www.epo.org/searching.html ), United States Patent and Trademark Office ( https://patft.uspto.gov/ ), the World Intellectual Property Organization's PATENTSCOPE ( https://patentscope.wipo.int/search/en/structuredSearch.jsf ), Google Patent ( https://www.google.com/?tbm=pts ), and China National Intellectual Property Administration ( https://pss-system.cponline.cnipa.gov.cn/conventionalSearch ). According to Cerimi et al. [ 41 ], the retrieved data and analysed may include the patent number, patent status, filing date, application date, grant dates, inventor, assignee, and pending applications. While data analysis is usually carried out by general data software such as Microsoft Excel, an intelligence software solely dedicated to patent research and analysis, Orbit Intelligence has been found to be more efficient [ 39 ]. It is also mandatory to include a methodology section in a patent review, and this should be explicit, thorough, and precise to allow a clear understanding of how the analysis was carried out and how the conclusions were arrived at.

4. Searching Literature

One of the most challenging tasks in writing a review article on a subject is the search for relevant literature to populate the manuscript as the author is required to garner information from an endless number of sources. This is even more challenging as research outputs have been increasing astronomically, especially in the last decade, with thousands of new articles published annually in various fields. It is therefore imperative that the author must not only be aware of the overall trajectory in a field of investigation but must also be cognizant of recent studies so as not to publish outdated research or review articles. Basically, the search for the literature involves a coherent conceptual structuring of the topic itself and a thorough collation of evidence under the common themes which might reflect the histories, conflicts, standoffs, revolutions, and/or evolutions in the field [ 7 ]. To start the search process, the author must carefully identify and select broad keywords relevant to the subject; subsequently, the keywords should be developed to refine the search into specific subheadings that would facilitate the structure of the review.

Two main tactics have been identified for searching the literature, namely, systematic and snowballing [ 42 ]. The systematic approach involves searching literature with specific keywords (for example, cancer, antioxidant, and nanoparticles), which leads to an almost unmanageable and overwhelming list of possible sources [ 43 ]. The snowballing approach, however, involves the identification of a particular publication, followed by the compilation of a bibliography of articles based on the reference list of the identified publication [ 44 ]. Many times, it might be necessary to combine both approaches, but irrespective, the author must keep an accurate track and record of papers cited in the search. A simple and efficient strategy for populating the bibliography of review articles is to go through the abstract (and sometimes the conclusion) of a paper; if the abstract is related to the topic of discourse, the author might go ahead and read the entire article; otherwise, he/she is advised to move on [ 45 ]. Winchester and Salji [ 5 ] noted that to learn the background of the subject/topic to be reviewed, starting literature searches with academic textbooks or published review articles is imperative, especially for beginners. Furthermore, it would also assist in compiling the list of keywords, identifying areas of further exploration, and providing a glimpse of the current state of the research. However, past reviews ideally are not to serve as the foundation of a new review as they are written from someone else's viewpoint, which might have been tainted with some bias. Fortunately, the accessibility and search for the literature have been made relatively easier than they were a few decades ago as the current information age has placed an enormous volume of knowledge right at our fingertips [ 46 ]. Nevertheless, when gathering the literature from the Internet, authors should exercise utmost caution as much of the information may not be verified or peer-reviewed and thus may be unregulated and unreliable. For instance, Wikipedia, despite being a large repository of information with more than 6.7 million articles in the English language alone, is considered unreliable for scientific literature reviews, due to its openness to public editing [ 47 ]. However, in addition to peer-reviewed journal publications—which are most ideal—reviews can also be drawn from a wide range of other sources such as technical documents, in-house reports, conference abstracts, and conference proceedings. Similarly, “Google Scholar”—as against “Google” and other general search engines—is more appropriate as its searches are restricted to only academic articles produced by scholarly societies or/and publishers [ 48 ]. Furthermore, the various electronic databases, such as ScienceDirect, Web of Science, PubMed, and MEDLINE, many of which focus on specific fields of research, are also ideal options [ 49 ]. Advancement in computer indexing has remarkably expanded the ease and ability to search large databases for every potentially relevant article. In addition to searching by topic, literature search can be modified by time; however, there must be a balance between old papers and recent ones. The general consensus in science is that publications less than five years old are considered recent.

It is important, especially in systematic reviews and meta-analyses, that the specific method of running the computer searches be properly documented as there is the need to include this in the method (methodology) section of such papers. Typically, the method details the keywords, databases explored, search terms used, and the inclusion/exclusion criteria applied in the selection of data and any other specific decision/criteria. All of these will ensure the reproducibility and thoroughness of the search and the selection procedure. However, Randolph [ 10 ] noted that Internet searches might not give the exhaustive list of articles needed for a review article; hence, it is advised that authors search through the reference lists of articles that were obtained initially from the Internet search. After determining the relevant articles from the list, the author should read through the references of these articles and repeat the cycle until saturation is reached [ 10 ]. After populating the articles needed for the literature review, the next step is to analyse them individually and in their whole entirety. A systematic approach to this is to identify the key information within the papers, examine them in depth, and synthesise original perspectives by integrating the information and making inferences based on the findings. In this regard, it is imperative to link one source to the other in a logical manner, for instance, taking note of studies with similar methodologies, papers that agree, or results that are contradictory [ 42 ].

5. Structuring the Review Article

The title and abstract are the main selling points of a review article, as most readers will only peruse these two elements and usually go on to read the full paper if they are drawn in by either or both of the two. Tullu [ 50 ] recommends that the title of a scientific paper “should be descriptive, direct, accurate, appropriate, interesting, concise, precise, unique, and not be misleading.” In addition to providing “just enough details” to entice the reader, words in the titles are also used by electronic databases, journal websites, and search engines to index and retrieve a particular paper during a search [ 51 ]. Titles are of different types and must be chosen according to the topic under review. They are generally classified as descriptive, declarative, or interrogative and can also be grouped into compound, nominal, or full-sentence titles [ 50 ]. The subject of these categorisations has been extensively discussed in many articles; however, the reader must also be aware of the compound titles, which usually contain a main title and a subtitle. Typically, subtitles provide additional context—to the main title—and they may specify the geographic scope of the research, research methodology, or sample size [ 52 ].

Just like primary research articles, there are many debates about the optimum length of a review article's title. However, the general consensus is to keep the title as brief as possible while not being too general. A title length between 10 and 15 words is recommended, since longer titles can be more challenging to comprehend. Paiva et al. [ 53 ] observed that articles which contain 95 characters or less get more views and citations. However, emphasis must be placed on conciseness as the audience will be more satisfied if they can understand what exactly the review has contributed to the field, rather than just a hint about the general topic area. Authors should also endeavour to stick to the journal's specific requirements, especially regarding the length of the title and what they should or should not contain [ 9 ]. Thus, avoidance of filler words such as “a review on/of,” “an observation of,” or “a study of” is a very simple way to limit title length. In addition, abbreviations or acronyms should be avoided in the title, except the standard or commonly interpreted ones such as AIDS, DNA, HIV, and RNA. In summary, to write an effective title, the authors should consider the following points. What is the paper about? What was the methodology used? What were the highlights and major conclusions? Subsequently, the author should list all the keywords from these answers, construct a sentence from these keywords, and finally delete all redundant words from the sentence title. It is also possible to gain some ideas by scanning indices and article titles in major journals in the field. It is important to emphasise that a title is not chosen and set in stone, and the title is most likely to be continually revised and adjusted until the end of the writing process.

5.2. Abstract

The abstract, also referred to as the synopsis, is a summary of the full research paper; it is typically independent and can stand alone. For most readers, a publication does not exist beyond the abstract, partly because abstracts are often the only section of a paper that is made available to the readers at no cost, whereas the full paper may attract a payment or subscription [ 54 ]. Thus, the abstract is supposed to set the tone for the few readers who wish to read the rest of the paper. It has also been noted that the abstract gives the first impression of a research work to journal editors, conference scientific committees, or referees, who might outright reject the paper if the abstract is poorly written or inadequate [ 50 ]. Hence, it is imperative that the abstract succinctly represents the entire paper and projects it positively. Just like the title, abstracts have to be balanced, comprehensive, concise, functional, independent, precise, scholarly, and unbiased and not be misleading [ 55 ]. Basically, the abstract should be formulated using keywords from all the sections of the main manuscript. Thus, it is pertinent that the abstract conveys the focus, key message, rationale, and novelty of the paper without any compromise or exaggeration. Furthermore, the abstract must be consistent with the rest of the paper; as basic as this instruction might sound, it is not to be taken for granted. For example, a study by Vrijhoef and Steuten [ 56 ] revealed that 18–68% of 264 abstracts from some scientific journals contained information that was inconsistent with the main body of the publications.

Abstracts can either be structured or unstructured; in addition, they can further be classified as either descriptive or informative. Unstructured abstracts, which are used by many scientific journals, are free flowing with no predefined subheadings, while structured abstracts have specific subheadings/subsections under which the abstract needs to be composed. Structured abstracts have been noted to be more informative and are usually divided into subsections which include the study background/introduction, objectives, methodology design, results, and conclusions [ 57 ]. No matter the style chosen, the author must carefully conform to the instructions provided by the potential journal of submission, which may include but are not limited to the format, font size/style, word limit, and subheadings [ 58 ]. The word limit for abstracts in most scientific journals is typically between 150 and 300 words. It is also a general rule that abstracts do not contain any references whatsoever.

Typically, an abstract should be written in the active voice, and there is no such thing as a perfect abstract as it could always be improved on. It is advised that the author first makes an initial draft which would contain all the essential parts of the paper, which could then be polished subsequently. The draft should begin with a brief background which would lead to the research questions. It might also include a general overview of the methodology used (if applicable) and importantly, the major results/observations/highlights of the review paper. The abstract should end with one or few sentences about any implications, perspectives, or future research that may be developed from the review exercise. Finally, the authors should eliminate redundant words and edit the abstract to the correct word count permitted by the journal [ 59 ]. It is always beneficial to read previous abstracts published in the intended journal, related topics/subjects from other journals, and other reputable sources. Furthermore, the author should endeavour to get feedback on the abstract especially from peers and co-authors. As the abstract is the face of the whole paper, it is best that it is the last section to be finalised, as by this time, the author would have developed a clearer understanding of the findings and conclusions of the entire paper.

5.3. Graphical Abstracts

Since the mid-2000s, an increasing number of journals now require authors to provide a graphical abstract (GA) in addition to the traditional written abstract, to increase the accessibility of scientific publications to readers [ 60 ]. A study showed that publications with GA performed better than those without it, when the abstract views, total citations, and downloads were compared [ 61 ]. However, the GA should provide “a single, concise pictorial, and visual summary of the main findings of an article” [ 62 ]. Although they are meant to be a stand-alone summary of the whole paper, it has been noted that they are not so easily comprehensible without having read through the traditionally written abstract [ 63 ]. It is important to note that, like traditional abstracts, many reputable journals require GAs to adhere to certain specifications such as colour, dimension, quality, file size, and file format (usually JPEG/JPG, PDF, PNG, or TIFF). In addition, it is imperative to use engaging and accurate figures, all of which must be synthesised in order to accurately reflect the key message of the paper. Currently, there are various online or downloadable graphical tools that can be used for creating GAs, such as Microsoft Paint or PowerPoint, Mindthegraph, ChemDraw, CorelDraw, and BioRender.

5.4. Keywords

As a standard practice, journals require authors to select 4–8 keywords (or phrases), which are typically listed below the abstract. A good set of keywords will enable indexers and search engines to find relevant papers more easily and can be considered as a very concise abstract [ 64 ]. According to Dewan and Gupta [ 51 ], the selection of appropriate keywords will significantly enhance the retrieval, accession, and consequently, the citation of the review paper. Ideally, keywords can be variants of the terms/phrases used in the title, the abstract, and the main text, but they should ideally not be the exact words in the main title. Choosing the most appropriate keywords for a review article involves listing down the key terms and phrases in the article, including abbreviations. Subsequently, a quick review of the glossary/vocabulary/term list or indexing standard in the specific discipline will assist in selecting the best and most precise keywords that match those used in the databases from the list drawn. In addition, the keywords should not be broad or general terms (e.g., DNA, biology, and enzymes) but must be specific to the field or subfield of study as well as to the particular paper [ 65 ].

5.5. Introduction

The introduction of an article is the first major section of the manuscript, and it presents basic information to the reader without compelling them to study past publications. In addition, the introduction directs the reader to the main arguments and points developed in the main body of the article while clarifying the current state of knowledge in that particular area of research [ 12 ]. The introduction part of a review article is usually sectionalised into background information, a description of the main topic and finally a statement of the main purpose of the review [ 66 ]. Authors may begin the introduction with brief general statements—which provide background knowledge on the subject matter—that lead to more specific ones [ 67 ]. It is at this point that the reader's attention must be caught as the background knowledge must highlight the importance and justification for the subject being discussed, while also identifying the major problem to be addressed [ 68 ]. In addition, the background should be broad enough to attract even nonspecialists in the field to maximise the impact and widen the reach of the article. All of these should be done in the light of current literature; however, old references may also be used for historical purposes. A very important aspect of the introduction is clearly stating and establishing the research problem(s) and how a review of the particular topic contributes to those problem(s). Thus, the research gap which the paper intends to fill, the limitations of previous works and past reviews, if available, and the new knowledge to be contributed must all be highlighted. Inadequate information and the inability to clarify the problem will keep readers (who have the desire to obtain new information) from reading beyond the introduction [ 69 ]. It is also pertinent that the author establishes the purpose of reviewing the literature and defines the scope as well as the major synthesised point of view. Furthermore, a brief insight into the criteria used to select, evaluate, and analyse the literature, as well as the outline or sequence of the review, should be provided in the introduction. Subsequently, the specific objectives of the review article must be presented. The last part of the “introduction” section should focus on the solution, the way forward, the recommendations, and the further areas of research as deduced from the whole review process. According to DeMaria [ 70 ], clearly expressed or recommended solutions to an explicitly revealed problem are very important for the wholesomeness of the “introduction” section. It is believed that following these steps will give readers the opportunity to track the problems and the corresponding solution from their own perspective in the light of current literature. As against some suggestions that the introduction should be written only in present tenses, it is also believed that it could be done with other tenses in addition to the present tense. In this regard, general facts should be written in the present tense, specific research/work should be in the past tense, while the concluding statement should be in the past perfect or simple past. Furthermore, many of the abbreviations to be used in the rest of the manuscript and their explanations should be defined in this section.

5.6. Methodology

Writing a review article is equivalent to conducting a research study, with the information gathered by the author (reviewer) representing the data. Like all major studies, it involves conceptualisation, planning, implementation, and dissemination [ 71 ], all of which may be detailed in a methodology section, if necessary. Hence, the methodological section of a review paper (which can also be referred to as the review protocol) details how the relevant literature was selected and how it was analysed as well as summarised. The selection details may include, but are not limited to, the database consulted and the specific search terms used together with the inclusion/exclusion criteria. As earlier highlighted in Section 3 , a description of the methodology is required for all types of reviews except for narrative reviews. This is partly because unlike narrative reviews, all other review articles follow systematic approaches which must ensure significant reproducibility [ 72 ]. Therefore, where necessary, the methods of data extraction from the literature and data synthesis must also be highlighted as well. In some cases, it is important to show how data were combined by highlighting the statistical methods used, measures of effect, and tests performed, as well as demonstrating heterogeneity and publication bias [ 73 ].

The methodology should also detail the major databases consulted during the literature search, e.g., Dimensions, ScienceDirect, Web of Science, MEDLINE, and PubMed. For meta-analysis, it is imperative to highlight the software and/or package used, which could include Comprehensive Meta-Analysis, OpenMEE, Review Manager (RevMan), Stata, SAS, and R Studio. It is also necessary to state the mathematical methods used for the analysis; examples of these include the Bayesian analysis, the Mantel–Haenszel method, and the inverse variance method. The methodology should also state the number of authors that carried out the initial review stage of the study, as it has been recommended that at least two reviews should be done blindly and in parallel, especially when it comes to the acquisition and synthesis of data [ 74 ]. Finally, the quality and validity assessment of the publication used in the review must be stated and well clarified [ 73 ].

5.7. Main Body of the Review

Ideally, the main body of a publishable review should answer these questions: What is new (contribution)? Why so (logic)? So what (impact)? How well it is done (thoroughness)? The flow of the main body of a review article must be well organised to adequately maintain the attention of the readers as well as guide them through the section. It is recommended that the author should consider drawing a conceptual scheme of the main body first, using methods such as mind-mapping. This will help create a logical flow of thought and presentation, while also linking the various sections of the manuscript together. According to Moreira [ 75 ], “reports do not simply yield their findings, rather reviewers make them yield,” and thus, it is the author's responsibility to transform “resistant” texts into “docile” texts. Hence, after the search for the literature, the essential themes and key concepts of the review paper must be identified and synthesised together. This synthesis primarily involves creating hypotheses about the relationships between the concepts with the aim of increasing the understanding of the topic being reviewed. The important information from the various sources should not only be summarised, but the significance of studies must be related back to the initial question(s) posed by the review article. Furthermore, MacLure [ 76 ] stated that data are not just to be plainly “extracted intact” and “used exactly as extracted,” but must be modified, reconfigured, transformed, transposed, converted, tabulated, graphed, or manipulated to enable synthesis, combination, and comparison. Therefore, different pieces of information must be extracted from the reports in which they were previously deposited and then refined into the body of the new article [ 75 ]. To this end, adequate comparison and combination might require that “qualitative data be quantified” or/and “quantitative data may be qualitized” [ 77 ]. In order to accomplish all of these goals, the author may have to transform, paraphrase, generalize, specify, and reorder the text [ 78 ]. For comprehensiveness, the body paragraphs should be arranged in a similar order as it was initially stated in the abstract or/and introduction. Thus, the main body could be divided into thematic areas, each of which could be independently comprehensive and treated as a mini review. Similarly, the sections can also be arranged chronologically depending on the focus of the review. Furthermore, the abstractions should proceed from a wider general view of the literature being reviewed and then be narrowed down to the specifics. In the process, deep insights should also be provided between the topic of the review and the wider subject area, e.g., fungal enzymes and enzymes in general. The abstractions must also be discussed in more detail by presenting more specific information from the identified sources (with proper citations of course!). For example, it is important to identify and highlight contrary findings and rival interpretations as well as to point out areas of agreement or debate among different bodies of literature. Often, there are previous reviews on the same topic/concept; however, this does not prevent a new author from writing one on the same topic, especially if the previous reviews were written many years ago. However, it is important that the body of the new manuscript be written from a new angle that was not adequately covered in the past reviews and should also incorporate new studies that have accumulated since the last review(s). In addition, the new review might also highlight the approaches, limitations, and conclusions of the past studies. But the authors must not be excessively critical of the past reviews as this is regarded by many authors as a sign of poor professionalism [ 3 , 79 ]. Daft [ 79 ] emphasized that it is more important for a reviewer to state how their research builds on previous work instead of outright claiming that previous works are incompetent and inadequate. However, if a series of related papers on one topic have a common error or research flaw that needs rectification, the reviewer must point this out with the aim of moving the field forward [ 3 ]. Like every other scientific paper, the main body of a review article also needs to be consistent in style, for example, in the choice of passive vs. active voice and present vs. past tense. It is also important to note that tables and figures can serve as a powerful tool for highlighting key points in the body of the review, and they are now considered core elements of reviews. For more guidance and insights into what should make up the contents of a good review article, readers are also advised to get familiarised with the Boote and Beile [ 80 ] literature review scoring rubric as well as the review article checklist of Short [ 81 ].

5.8. Tables and Figures

An ideal review article should be logically structured and efficiently utilise illustrations, in the form of tables and figures, to convey the key findings and relationships in the study. According to Tay [ 13 ], illustrations often take a secondary role in review papers when compared to primary research papers which are focused on illustrations. However, illustrations are very important in review articles as they can serve as succinct means of communicating major findings and insights. Franzblau and Chung [ 82 ] pointed out that illustrations serve three major purposes in a scientific article: they simplify complex data and relationships for better understanding, they minimise reading time by summarising and bringing to focus on the key findings (or trends), and last, they help to reduce the overall word count. Hence, inserting and constructing illustrations in a review article is as meticulous as it is important. However, important decisions should be made on whether the charts, figures, or tables to be potentially inserted in the manuscript are indeed needed and how best to design them [ 83 ]. Illustrations should enhance the text while providing necessary information; thus, the information described in illustrations should not contradict that in the main text and should also not be a repetition of texts [ 84 ]. Furthermore, illustrations must be autonomous, meaning they ought to be intelligible without having to read the text portion of the manuscript; thus, the reader does not have to flip back and forth between the illustration and the main text in order to understand it [ 85 ]. It should be noted that tables or figures that directly reiterate the main text or contain extraneous information will only make a mess of the manuscript and discourage readers [ 86 ].

Kotz and Cals [ 87 ] recommend that the layout of tables and figures should be carefully designed in a clear manner with suitable layouts, which will allow them to be referred to logically and chronologically in the text. In addition, illustrations should only contain simple text, as lengthy details would contradict their initial objective, which was to provide simple examples or an overview. Furthermore, the use of abbreviations in illustrations, especially tables, should be avoided if possible. If not, the abbreviations should be defined explicitly in the footnotes or legends of the illustration [ 88 ]. Similarly, numerical values in tables and graphs should also be correctly approximated [ 84 ]. It is recommended that the number of tables and figures in the manuscript should not exceed the target journal's specification. According to Saver [ 89 ], they ideally should not account for more than one-third of the manuscript. Finally, the author(s) must seek permission and give credits for using an already published illustration when necessary. However, none of these are needed if the graphic is originally created by the author, but if it is a reproduced or an adapted illustration, the author must obtain permission from the copyright owner and include the necessary credit. One of the very important tools for designing illustrations is Creative Commons, a platform that provides a wide range of creative works which are available to the public for use and modification.

5.9. Conclusion/Future Perspectives

It has been observed that many reviews end abruptly with a short conclusion; however, a lot more can be included in this section in addition to what has been said in the major sections of the paper. Basically, the conclusion section of a review article should provide a summary of key findings from the main body of the manuscript. In this section, the author needs to revisit the critical points of the paper as well as highlight the accuracy, validity, and relevance of the inferences drawn in the article review. A good conclusion should highlight the relationship between the major points and the author's hypothesis as well as the relationship between the hypothesis and the broader discussion to demonstrate the significance of the review article in a larger context. In addition to giving a concise summary of the important findings that describe current knowledge, the conclusion must also offer a rationale for conducting future research [ 12 ]. Knowledge gaps should be identified, and themes should be logically developed in order to construct conceptual frameworks as well as present a way forward for future research in the field of study [ 11 ].

Furthermore, the author may have to justify the propositions made earlier in the manuscript, demonstrate how the paper extends past research works, and also suggest ways that the expounded theories can be empirically examined [ 3 ]. Unlike experimental studies which can only draw either a positive conclusion or ambiguous failure to reject the null hypothesis, four possible conclusions can be drawn from review articles [ 1 ]. First, the theory/hypothesis propounded may be correct after being proven from current evidence; second, the hypothesis may not be explicitly proven but is most probably the best guess. The third conclusion is that the currently available evidence does not permit a confident conclusion or a best guess, while the last conclusion is that the theory or hypothesis is false [ 1 ]. It is important not to present new information in the conclusion section which has link whatsoever with the rest of the manuscript. According to Harris et al. [ 90 ], the conclusions should, in essence, answer the question: if a reader were to remember one thing about the review, what would it be?

5.10. References

As it has been noted in different parts of this paper, authors must give the required credit to any work or source(s) of information that was included in the review article. This must include the in-text citations in the main body of the paper and the corresponding entries in the reference list. Ideally, this full bibliographical list is the last part of the review article, and it should contain all the books, book chapters, journal articles, reports, and other media, which were utilised in the manuscript. It has been noted that most journals and publishers have their own specific referencing styles which are all derived from the more popular styles such as the American Psychological Association (APA), Chicago, Harvard, Modern Language Association (MLA), and Vancouver styles. However, all these styles may be categorised into either the parenthetical or numerical referencing style. Although a few journals do not have strict referencing rules, it is the responsibility of the author to reference according to the style and instructions of the journal. Omissions and errors must be avoided at all costs, and this can be easily achieved by going over the references many times for due diligence [ 11 ]. According to Cronin et al. [ 12 ], a separate file for references can be created, and any work used in the manuscript can be added to this list immediately after being cited in the text [ 12 ]. In recent times, the emergence of various referencing management software applications such as Endnote, RefWorks, Mendeley, and Zotero has even made referencing easier. The majority of these software applications require little technical expertise, and many of them are free to use, while others may require a subscription. It is imperative, however, that even after using these software packages, the author must manually curate the references during the final draft, in order to avoid any errors, since these programs are not impervious to errors, particularly formatting errors.

6. Concluding Remarks

Writing a review article is a skill that needs to be learned; it is a rigorous but rewarding endeavour as it can provide a useful platform to project the emerging researcher or postgraduate student into the gratifying world of publishing. Thus, the reviewer must develop the ability to think critically, spot patterns in a large volume of information, and must be invested in writing without tiring. The prospective author must also be inspired and dedicated to the successful completion of the article while also ensuring that the review article is not just a mere list or summary of previous research. It is also important that the review process must be focused on the literature and not on the authors; thus, overt criticism of existing research and personal aspersions must be avoided at all costs. All ideas, sentences, words, and illustrations should be constructed in a way to avoid plagiarism; basically, this can be achieved by paraphrasing, summarising, and giving the necessary acknowledgments. Currently, there are many tools to track and detect plagiarism in manuscripts, ensuring that they fall within a reasonable similarity index (which is typically 15% or lower for most journals). Although the more popular of these tools, such as Turnitin and iThenticate, are subscription-based, there are many freely available web-based options as well. An ideal review article is supposed to motivate the research topic and describe its key concepts while delineating the boundaries of research. In this regard, experience-based information on how to methodologically develop acceptable and impactful review articles has been detailed in this paper. Furthermore, for a beginner, this guide has detailed “the why” and “the how” of authoring a good scientific review article. However, the information in this paper may as a whole or in parts be also applicable to other fields of research and to other writing endeavours such as writing literature review in theses, dissertations, and primary research articles. Finally, the intending authors must put all the basic rules of scientific writing and writing in general into cognizance. A comprehensive study of the articles cited within this paper and other related articles focused on scientific writing will further enhance the ability of the motivated beginner to deliver a good review article.

Acknowledgments

This work was supported by the National Research Foundation of South Africa under grant number UID 138097. The authors would like to thank the Durban University of Technology for funding the postdoctoral fellowship of the first author, Dr. Ayodeji Amobonye.

Data Availability

Conflicts of interest.

The authors declare that they have no conflicts of interest.

How to... Understand the peer review process

The peer review process followed depends on the channel the author chooses for their research. We highlight the two models used by our journals, cases, and open research platform.

On this page

The peer review process, peer review models, our approach to article peer review.

Download and keep your step-by-step guide (PDF), or view the accessible version of the flowchart below.

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Accessible version of content

Peer review process .

Submission 

1. The editor rejects the submission if it doesn’t meet the journal’s editorial objectives. 

2. The editor selects up to three reviewers and asks them to evaluate the manuscript against a set of criteria. 

3. The editor receives the reviewers’ recommendations.

4. The editor makes the final decision, taking into account the reviewers’ recommendations. Go to 5 if accepted, 6 if rejected, or 7 if revisions are required.

Accept 

5. The editor notifies the author that their paper has been accepted > Publish

6. The editor notifies the author that their paper has been rejected and shares a copy of the reviewers’ comments > Reject

Revise 

7. The editor notifies the author that their paper requires revisions and shares a copy of the reviewers’ comments.

8. The author resubmits their revised paper.

9. The editor can either make a decision based on the revised paper or send the revised paper to the same reviewers. Go to 3.

Single-anonymous peer review

The names of the reviewers are hidden from the author. However, the name of the author is shared with the reviewers.

The fact that reviewers remain anonymous means they can speak honestly and impartially. Meanwhile, knowledge of an author’s identity can help reviewers place an article in the context of the author’s earlier work.

Double-anonymous peer review

The reviewers aren’t told the name of the author, and the author never learns the names of the reviewers.

Outside of the triple-anonymous model (see below), this is the surest way to ensure that the process is completely objective.

The focus remains on the content of the article, and the possibility of reviewer bias is eliminated. Reviewer bias may be favourable or unfavourable, conscious or unconscious.

Triple-anonymous peer review

The identities of the author, reviewers and editors remain hidden from each other. The author is usually identified only by a number and communication takes place through a website or submission system. This eliminates any potential bias.

Open peer review

This can vary in form. It may be as simple as making the author and reviewers known to one another, or the reviews – and the reviewers’ names – may be published alongside the article. The review process may take place pre- or post-publication, and reports may receive their own DOIs, making them discoverable and citable.

This offers complete transparency. Some believe that the knowledge that reports are going to be published encourages reviewers to produce higher-quality reports overall. The post-publication format publicly recognises the important work of the reviewers.

The majority of our journals have adopted a double-anonymous peer review model, with reviewers invited by the journal editor.

Quality peer review is constructive, non-confrontational and prompt. It means putting yourself in the position of the author and helping them to bring out the best in their paper.

Related topics

Reviewer hub.

Here you will find practical tips and guidance on all aspects of peer review. 

Become a reviewer

Whether this is your first time reviewing or you are a seasoned professional, we explain why you should say yes next time an editor asks you to review.

Reviewer guidelines

Our reviewers play a crucial role in the publication process with a wide range of responsibilities. We have developed some reviewer guidelines to support you at each stage of the process.

How to Do Great Research

Grad school survival advice from nick feamster and alex gray.

• The Paper Reviewing Process

Learning how to review papers not only (obviously) makes you a better reviewer, but it can also help you as an author, since an understanding of the process can help you write your paper submissions for an audience of reviewers.  If you know the criteria that a reviewer will use to judge your paper, you are in a much better position to tailor your paper so that it has a higher chance of being accepted.

There are many good resources that describe the paper reviewing process already, including those that explain the process (and its imperfections) and those that provide instructions for writing a good review (as well as techniques to avoid ).  There are also a few nice summaries of the review process for conferences in different areas of computer science that lend visibility into the process (e.g., here and here ).  Program committee chairs sometimes provide guidelines for writing reviews, such as these .  I will not reiterate or summarize those previous articles here, but they are all definitely worth a read.  Instead, I will discuss the importance of the review process and how it differs from simply reading a paper; I’ll also talk about how to prepare (and ultimately write) a review.

I will not talk about the paper  selection process  (i.e., what determines whether a paper is ultimately accepted or rejected), but will instead focus on the creation of a paper review.  Program committee meetings are an important part of the paper  selection  process—at least in computer science—and I will be devoting a complete post to this topic next week.  Meanwhile, I recommend reading  Matt Welsh’s post on the psychology of program committees .

The Review Process

Why understanding the review process is important.  Whether you end up reviewing a lot of papers as a Ph.D. student, your research will definitely be subject to the paper review process.  It is imperative as a researcher to understand this process.  Knowing the process can help you better write your paper for an audience of reviewers (and a program committee), and it can also help you maintain perspective when your paper is accepted or rejected.   The process is far from perfect, and the outcome of the process is neither validation nor condemnation of your work.   How you react—and how you adapt your research or follow through on it after the acceptance (or rejection)—is far more important to long-term success.

In the “Introduction to the Ph.D.” class at Georgia Tech, I ask students to create a research idea and write it up; a subsequent set of assignments asks the students to review and evaluate the ideas as part of a “mock” program committee.  The process isn’t exactly the same as the review process for a full paper, but it is a lightweight way to have students experience the process first-hand in a low-stakes setting, and see both sides of the process (submission and review) at the same time.  In next week’s blog post, I will discuss program committee meetings in general, as well as some observations from this year’s (and previous years’) in-class experiences with the mock PC.

Reviewing vs. reading.   There are some significant distinctions between reading papers vs. reviewing them.  When reading a paper for your own enrichment, your goal is to gather information as quickly as possible.  In this case, you are a  scientist  who seeks to understand the context and content of existing work, to (for example) better understand how your own research might fit into the bigger picture or learn about techniques that might apply to your own work.  The goal of reviewing is different.  A reviewer’s goal is to first and foremost determine the suitability of a paper for some conference and second, to provide feedback to the authors to help them improve the paper in subsequent revisions.  Remember that the reviewer’s primary goal trumps all other objectives: A reviewer often has a large number of papers to process and is typically not deeply devoted to improving the content of any particular paper.  If you are lucky, you will get a diligent, thoughtful reviewer who provides thorough feedback, but do not be surprised if a review is not as thorough as you would have liked, or if the review “misses” some point you were trying to make.  We would all like reviewers to make three passes through your paper submission —and, these are the instructions I would give, too, in an ideal world.  Unfortunately, however, you will be lucky in many cases to get two thorough reads.  The reviewer’s main goal is to determine the paper’s suitability for publication.  As an author, you shouldn’t be surprised if some of the comments seem trivial: there may be underlying issues of  taste  that drove the reviewer’s opinion on your paper that a reviewer may not explicitly state.  Whenever I read reviews I receive for a rejected paper, I try to look past specific detailed quibbles (or “excuses” for rejecting the paper) and figure out the big picture:  the reviewer couldn’t find a reason to accept the paper.

Calibration: Reviewing one paper vs. reviewing many papers. The paper review process can differ depending on who, exactly, is reviewing the paper.  For example, as a Ph.D. student, you may review one or two papers at a time, as an “external reviewer” for a conference or journal.  Journal editors and program committee chairs often seek the help of external reviewers if they need a particular subject-matter expert to review a paper.  Later in your Ph.D. career, you may have established yourself as an expert on a particular topic and find yourself reviewing a paper here and there on a handful of topics.  Sometimes a member of the program committee (e.g., your advisor) might ask you to help review a particular paper.  As you progress in your career, you will be asked to serve on program committees yourself, whereupon you’ll find yourself with tens of papers to review over the course of a couple of months.  Ironically, it is sometimes easier to review a group of papers than a single (or a few) papers, because seeing a group of papers helps you “calibrate” your scores and rankings of papers according to the general quality of papers that have been submitted to the conference.    If you have been asked to review a single paper for a conference, you should either figure out how to calibrate your assessment with respect to other papers that might have been submitted, or simply review the paper on its merits while reserving judgement as to the paper’s ultimate disposition.

Does the Paper Realize a Great Idea?

Look for a reason to accept the paper.  Does it realize a great contribution or idea?   Every paper is imperfect.  The paper may have made an incorrect or imperfect assumption.  The experiments may not have been as thorough as you liked.  The graphs may be difficult to read.  Parts of the paper may be difficult to understand.  These types of issues certainly reflect problems with a paper, but they do not necessarily constitute a reason to reject a paper if they do not affect the correctness or significance of the main underlying conclusion or contribution of the paper.  Therefore, the first two questions I ask myself when reviewing a paper are: (1) Does the paper have a great idea?; and (2) Does it  realize the great idea?  (or, alternatively, to what extent does it realize that great idea, since typically no paper is water-tight).

What makes an idea “great”?     Judging a paper’s contribution turns out to be highly subjective, which is why the review process remains so uncertain.  A paper isn’t judged on a set of fixed checkboxes, a grading “key”, or any notion of absolute correctness.  Reviewers often reserve considerable judgment based on “ taste “, and reasonable people will disagree as to the merits of the main contribution or idea in a paper.  In fact, there has been a fair amount of documentation that, as reviewers, we are often quite terrible at predicting the merits of a particular piece of submitted work:  There’s a great article on this topic , as well as some parodies  to illustrate the subjective nature of the process.  Many fields have also introduced a “ test of time ” award to papers from past decades, to recognize accepted papers that have truly had long-term positive impact (implicitly acknowledging that this is almost impossible to assess when a paper is first published).  Due to the subjective nature of this judgment, it is all the more important that your writing is clear , and well-matched to what a reviewer is looking for (i.e., the contributions and ideas).

Invariant questions.   Different conferences may have different value structures, and the chairs of any given conference may ask the reviewers to focus on different criteria when judging a paper.  Regardless, there are some invariant questions that most reviewers would (or at least should) always consider, including:

• Is the problem important?  What problem is the paper trying to solve, and is it important?  Seek to summarize the paper’s contribution in one sentence.  Make this short summary the beginning of your review, as well.  Try to convince yourself (by reading the paper or otherwise) that a solution to the problem that the paper is proposing would advance knowledge or significantly improve the state of affairs for some group of people.  Note that  you may not care about the problem, but also ask yourself whether you can imagine  some group of readers who will be interested in the solution to the problem. When asking yourself this question about a paper, try to divorce your own taste about the problem’s importance from the more general question concerning whether there is some group of people who would be interested in the problem the paper is addressing and solving.
• To what extent does the paper solve the problem it describes?   A single paper very rarely closes the book on a single problem, but it may take an important step towards solving the problem.  It might solve the problem for an important set of operating conditions or under a new set of assumptions.  Or, if the problem area is completely new, perhaps the paper doesn’t really solve the problem at all, but simply articulating a new problem area for follow-on work is a significant contribution.
• What is the “intellectual nugget”?   As a reviewer, I try to identify whether a paper has a particular intellectual kernel that lies at the heart of the solution.  This kernel is often what separates an important research contribution from a simple matter of engineering.  This intellectual nugget might be the application (or invention) of a particular technique, a proof of correctness (where one previously did not exist), or an attempt to put the solution into a broader intellectual context.  In other words, the intellectual contribution might be to take a general problem and tackle a specific sub-problem (e.g., under certain assumptions or conditions), or to take a specific problem and generalize it (e.g., develop a general theory, proof of correctness, or taxonomy).  Looking through the paper for applications of specific research patterns can help identify an intellectual nugget, if one exists.
• What is the main contribution or conclusion?  Is it important?   As a reviewer, I try to concisely articulate the paper’s main contribution (or small number of contributions).  Often, a paper will helpfully summarize those contributions somewhere in the introduction (Jim Kurose’s advice on writing paper introductions advises the writer to explicitly do so).   The reviewer’s job is then to assess whether those contributions are significant or important enough to warrant a publication.  The significance of those contributions often depends on the perceived increment over previous work.   All work is incremental to some degree , as everything builds on past work.  The author’s job is to convince the reviewer that the increment is important, and the reviewer’s job is to assess the author’s claims of significance.
• Does the content support the conclusion?  An introduction may make broad (or wild) claims, and it is important to dig into the paper to determine whether the content of the paper supports the conclusion.  Are the experiments run correctly?  Are they based on the correct set of assumptions?  If the conclusion involves comparison to previous work, is the comparison performed in a controlled manner, using an equivalent (or at least fair) experimental setup?  If applicable, have the authors released their code and data so that you (or others) can check the claims yourself?

Preparing Your Review

Consider the audience.   Not every publication venue is the same.  Some venues are explicitly geared towards acceptance of early, incomplete work that is likely to generate discussion (many workshops use this criterion for acceptance).  Other venues favor contributions that constitute well-executed, smaller increments.  When reviewing a paper, either externally or as a member of a committee, your first question should be to consider the audience for the conference, workshop, or journal, and whether the likely audience for the venue would benefit from reading the paper.  The question of audience involves that of both the “bar” for acceptance (Does the paper meet the audience’s standards for something that is worth reading?) and the “scope” of the venue (is the paper on-topic for the venue?).  Often, scope can be (and is) broadly construed, so the key question really boils down to whether the likely audience for the paper will benefit from reading it.

Consider the standards. Your standards will (and should) vary depending on the venue for which you are reviewing a paper submission.  Workshops are typically more permissive as far as accepting “vision” papers that outline a new problem or problem area or papers that “foster discussion” than conferences, which typically aim to accept more complete pieces of work.   Nevertheless, even the standards for a conference review process will vary depending on both the conference itself, the program committee chair’s instructions about how permissive to be, and the relative quality of the group of papers that you are reviewing.  A good way to get a sense for the standards of a conference for which you are reviewing is to  read through the complete set of papers that you have been asked to review and rank them,  before writing a single review.  This will ensure some level of calibration, although it is still biased based on the set of papers that you are reviewing.  Reading past proceedings of the particular journal or conference can also help you determine the appropriate standard to set for acceptance.

Consider the purpose.   Different papers serve different purposes.  Multiple paper submissions to the same venue might in fact have quite different purposes, and it is important to establish what the paper is contributing (or attempting to contribute) before passing judgement.  For example, a paper might be a complete piece of work, but it might also be a survey, a tutorial, or simply a proposal.  If the paper is one of the latter types, your first questions as a reviewer should concern whether the audience would benefit from the survey, tutorial, or proposal, and whether such a paper meets the standards for the conference.  If the answers to those questions are “yes”, then your evaluation should be tailored to the paper’s purpose.  If the paper is a survey, your assessment should be based on the completeness of the survey, with respect to the area that the paper is claiming to summarize.  If the paper is a tutorial, is the description correct and clearly described?  If the paper is a proposal , does the proposed research agenda make sense, and is the outcome (if the proposal is successful) worthwhile?

Consider the big picture.   Every paper can be rejected.  It is always easy to find reasons to reject a paper.  The reviewer’s goal should not be to identify the reasons to reject a paper, but rather to determine  whether there are any reasons to accept the paper.   If the answer to that question is negative, then it is always easy to find “excuses” to reject a paper (recall the discussion above).  You should be aiming to figure out whether the paper has important contributions that the audience will benefit from knowing about, and whether the paper supports those contributions and conclusions to the level of standard that is commensurate with the standard of the audience and the venue.  One litmus test I use to ensure that a negative aspect of a paper does not condemn it is to ask myself whether the problem (1) affects the main conclusion or contribution of the paper; and (2) can be fixed easily in a revision.   If the problem doesn’t affect the main contribution or conclusion, and if it can be easily fixed, then it should not negatively affect a paper’s review.

Writing Your Review

Start with a summary of the paper and its contributions.  A short, one-paragraph summary describing the paper’s main contribution(s) demonstrates to the authors (and to you!) that you understand the main point of the paper.  This helps you as a reviewer articulate the main contributions and conclusions of the paper for the purposes of your own evaluation.  Try to address the type of paper it is (is it a survey paper, for example?), the context for the paper (i.e., how it builds on or relates to previous work), its overall correctness, and its contributions.  If you cannot concisely summarize the paper, then the paper is not in good shape, and you can reflect this assessment in the review, as well.  These summaries are very helpful to authors, since they may not match the authors’ views of the main contribution!  For example, as an author, you can easily figure out if you’ve “missed the mark” or whether the reviewer fundamentally misunderstood the paper by reading a reviewer’s summary of your own work.  If the summary of the contribution does not match your own view of the paper’s contribution, then you know that you have some work to do in writing and presentation.

Assess whether the paper delivers on the main claims and contributions.   You should provide an assessment, for each of the paper’s main claims and contributions, whether it delivers on that claim.  If the main contribution of the paper is flawed, you should indicate whether you think a flaw is “fatal”, or whether the authors could simply fix the flaw in a revision if the paper is accepted.  Sometimes flaws (e.g., inconsistent terminology) are fixable. Other flaws (e.g., a questionable experimental setup) may or may not be fixable.  While it might seem that a broken experimental setup is “fatal”, ask yourself as a reviewer whether the conclusions from the paper’s experiments as is are still meaningful, even if the authors have not interpreted the results correctly.  If the conclusions from the experiments can be restated and still turn out to be meaningful contributions—or, if the flaw in an experiment doesn’t affect the main contribution or conclusion—then even a flaw in experiments can likely be fixed in revision.  Occasionally, however, experiments may need to be completely redesigned because they don’t support any meaningful conclusion.  Or, the content of the paper may simply be incorrect; sometimes correctness issues are difficult for a reviewer to spot, so a paper isn’t necessarily “correct” simply because a reviewer has validated the paper.  Regardless, if there are correctness issues that affect the main contribution of the paper that call into question whether the main result or contribution is correct in the first place, the paper’s review should reflect these concerns and likely cannot be accepted.

Discuss positive aspects of the paper; always try to find something positive, even in “bad” papers.  It is easy to identify problems with a paper.  It can be much trickier (especially with “average” papers) to identify the positive aspects and contributions, but most papers typically have at least some small kernel of goodness.  Even for particularly bad papers, there might be one sentence in the introduction, discussion, or future work section that makes an interesting point or highlights a possibility for interesting contributions.  In a pinch, if you can’t find anything positive, those are good places to look.  As a reviewer, you can remark that those observations are interesting, and that you would really like to see those parts of the work further developed.  These positive comments aren’t just for author morale (although that’s important, too): They give the author a direction to move forward.  The worst reviews are those that reject a paper but don’t provide any specific action for moving forward.  The best reviews are those that highlight the positive aspects of the work, while identifying weaknesses and areas where the work could be further developed to address weaknesses or build on the paper’s existing strengths.

Criticize the paper, not the authors.   When writing your review, consider the type of review that you would like to receive.  Always be polite, respectful, and positive.  Don’t be personal.   Choose your language carefully, as it will help convey your message.  For example, if you say “the authors don’t consider the related work”, that is a much more personal statement than “the paper doesn’t consider the related work”.  (In fact, you don’t know if the authors considered a particular piece of related work anyway; they may have simply chosen not to include it in the writeup!)  Talking about “the authors” gets personal, and it will put the authors themselves on the defensive when reading your review.  Instead, focus on “the paper” and frame your critique around “suggestions for improvement”.  Never, ever insult the authors; don’t accuse the authors of being sloppy or unethical researchers.  As a reviewer, you don’t always know the full context, so limit your judgement to what you can directly conclude by reading the paper.

Consider the type of feedback you would like to receive.   Receiving reviews for rejected papers is a part of the research process, but it is never fun for the authors (particularly new Ph.D. students). Do your part to contribute positively to the process by suggesting changes that you’d like to see if you had to review the paper again.  In all likelihood, you may see the paper again in the form of a revision!

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SOWK 210 Environmental Sustainability and Environmental Justice : Research Paper

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Empirical Studies

What are the different types of articles?  

• An empirical (research) article reports methods and findings of an original research study conducted by the authors. Empirical research relies on experience or involves observation
• A literature review discusses past research studies on a given topic and you can connect the studies thematically
• Conceptual research articles are related to an idea or theory. These type of articles  are used to develop new concepts or to reinterpret existing ones.

If you are not familiar with what empirical studies are and/or how to find them, the following links can be helpful:

• Social Work: Empirical Articles: Finding Empirical Articles  - a LibGuide from Georgia State University Library explaining what empirical studies are and where to find them
• My instructor said that I needed to find "Empirical" articles. What should I do? - from Cal Poly Pomona. Pay attention to #2 -- search devices in different databases. Ignore the Ask Us section on the right as it is information pertinent to their library.
• Empirical Research  - from CSU, Chicago, Meriam Library. Check out the Test your knowledge section
• Empirical Research in the Social Sciences and Education - a LibGuide from Penn State Libraries

Empirical Research: Finding Empirical Research in Library Databases  - note the keywords used for 'empirical studies' in ERIC and other medical databases

How to read a research paper?

• Anatomy of a Research Paper
• Anatomy of a Scientific Paper
• How do I begin  - helpful guide from Purdue OWL
• Research Paper, Qualitative Methodology, APA Style (Sociology)  - from Writer's Help Hacker Handbooks
• Example of Quantitative Paper   from Trinity Washington University
• On Methods: What’s the difference between qualitative and quantitative approaches? - from the Chronicle of Evidence-based Mentoring, U Mass Boston
• Social Work Literature Review Guidelines - from Perdue OWL
• Conceptual vs. Empirical Research: Which Is Better?  - from the enago academy

You may have an assignment that asks you to read a research paper and critique it. You start reading the paper but it is long and boring (!) and you may not have any clue how to comprehend it! 'How to Read a Paper' series from The BMJ is a go to source when it comes to learning how to read a research paper.

Here's the  link  to the following articles:

• Papers that go beyond numbers (qualitative research)  Trisha Greenhalgh, Rod Taylor
• Papers that summarise other papers (systematic reviews and meta-analyses)  Trisha Greenhalgh
• Papers that tell you what things cost (economic  analyses )   Trisha Greenhalgh
• Papers that report diagnostic or screening tests  Trisha Greenhalgh
• Papers that report drug trials   Trisha Greenhalgh
• Statistics for the non-statistician. II: "Significant" relations and their pitfalls  Trisha Greenhalgh
• Statistics for the non-statistician  Trisha Greenhalgh
• Assessing the methodological quality of published papers  Trisha Greenhalgh
• Getting your bearings (deciding what the paper is about)  Trisha Greenhalgh
• The Medline database  Trisha Greenhalgh

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Ammonia inhibition in anaerobic digestion of organic waste: a review

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• Published: 09 September 2024

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• J. Yang 1 , 2 ,
• J. Zhang 1 ,
• Z. Cheng 1 ,
• W. Fu 1 &
• S. Wang 1  

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Anaerobic digestion (AD) has become the technology of choice for organic waste treatment as an environmentally beneficial and sustainable waste treatment technology. However, the nitrogen content of these organic waste streams is generally high. Ammonia is produced in the biodegradation of nitrogenous organic matter. Low concentrations of ammonia favour AD, but high concentrations can lead to digestive system failure. To address the issue of ammonia inhibition and ensure the stability of the digestive system, numerous physical, chemical, and biologicalmethods aimed at controlling ammonia levels and/or strengthening the biological processes have been proposedand developed. Literature evidence suggests that differences in AD reaction conditions and microbial sources result in different tolerances of the digestive system to ammonia and nitrogen. This paper summarises and compares the inhibitory effects of ammonia nitrogen under different conditions and the existing regulatory measures to alleviate ammonia nitrogen inhibition. In addition, since the core of the digestive system is microorganisms, this paper explains the mechanism of ammonia stress especially at the microbial level, and in this way, it explores the future direction of research using biofortification. This review provides a theoretical reference for solving the problem of ammonia nitrogen inhibition.

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Introduction

As the global population continues to grow and the economy develops at a rapid pace, municipal solid waste (MSW) generation has surged worldwide. Currently, the global generation of MSW is about 2.01 billion tonnes per year (ranging from 0.11 to 4.54 kg/capita/day), but it is projected to increase to 3.40 billion tonnes by 2050 (Rosas-Mendoza et al. 2024 ). Most of this MSW is openly wasted and very little of it is converted into useful resources. An estimated 93% of waste is either dumped or incinerated, predominantly in less developed countries (Khurram et al. 2024 ). Organic waste (OW) accounts for 42–69 percent of MSW. These include crop residues, animal manure, landscaping waste, municipal sludge, animal inclusions from slaughterhouses, food waste, etc. (Pongsopon et al. 2023 ; Khurram et al. 2024 ). Inadequate management of organic waste can lead to various environmental hazards and even threaten human health. It is estimated that about 5% of total greenhouse gas emissions are due to open dumping of OW (Sailer et al. 2021 ).

How to properly deal with organic waste has become an important issue for human beings to solve at present, the current conventional treatment technology includes measures such as crushing direct discharge, landfill, incineration and so on (Guo et al. 2023 ) but faces the problem of secondary pollution from siltation and blockage of urban sewage network, leachate leakage and dioxin and greenhouse gas emissions. Anaerobic digestion of organic waste has received widespread attention as an eco-friendly and economically viable method. the technology has been applied to treat a variety of wastes, including municipal sludge, poultry manure, food/fermentation industry wastes, and concentrated municipal wastewater. (Tiwari et al. 2023 ; Rivera et al. 2023 ; Paranjpe et al. 2023 ).As of 2017, there were at least 118 kitchen waste treatment projects in China with a scale of 50 t/d or more, of which 76.1% used anaerobic digestion technology. From 2009 to 2020, the number of anaerobic digestion plants in Europe increased from 6,227 to 19,000 (Zhang et al. 2023 ). Simply put, anaerobic digestion relies on the synergistic action of hydrolysing acidifying microorganisms and methanogenic microorganisms, a process that converts organic matter into biogas, biogas residue and a carbon-rich fermentation broth. As the technology continues to mature, it has become a key technology for reducing organic waste, recovering biomass energy, and producing biofuels and energy (O'Connor et al. 2021 ). Research indicates that AD is highly effective for treating and managing OW (Granzotto et al. 2021 ).

Ammonia inhibition is a challenging issue in the AD of nitrogen-rich substrates(e.g.food waste and animal waste) and hindersthe energy recovery from organic wastes. Ammonia is produced by the biodegradation of nitrogenous organic matter in organic waste. The low concentrations of ammonia favor AD, but high concentrations of ammonia can lead to digestive system failure (Li et al.. 2023 ; O'Connor et al. 2023 ). The two main forms of total ammonia nitrogen (TAN) are ammonium ions (NH 4 + ) and free ammonia (NH 3 , FAN), both of which can directly or indirectly cause inhibition in AD systems (Lendormi et al. 2022 ; Mlinar et al. 2022 ). The relationship between the two is expressed in Eq. ( 1 ) (Xiao et al. 2022a ). Typically, FAN is considered the primary cause of inhibition because hydrophobic FAN molecules may passively diffuse through cellular membranes, leading to proton imbalance and/or potassium deficiency (Shi et al. 2017 ). Additionally, FAN enters microbial cells by passive diffusion and is subsequently converted to NH4 + through binding with extracellular protons (H + ), resulting in alterations in intracellular pH. To maintain intracellular proton homeostasis, cells actively transport potassium ions out of the cell via energy-consuming potassium pumps in the cell membrane. This process increases the energy required for cellular maintenance and limits certain specific enzymatic reactions(Mlinar et al. 2022 ; Peng et al. 2023a ). Various inhibitory thresholds of total ammonia nitrogen (TAN) concentrations, ranging from 3.4 to 5.77 gL −1 , have been reported, resulting in severe methane yield losses in the AD process ranging from 39 to 100% (Li et al. 2023 ). These outcome variations can be attributed to differences in temperature, reactor configuration, and the microbial communities that develop in distinct systems [Li et al. 2023 ].

Recent studies have focused on regulatory strategies to mitigate ammonia inhibition during anaerobic digestion (AD) of nitrogenous organic wastes. Various physical, chemical, and biological methods have been developed to control ammonia levels and enhance biological processes. Examples include substrate dilution, adjustment of the carbon to nitrogen ratio, pH control and ammonia recovery through membrane distillation, in addition, other methods have been tested to enhance the biological process including bioaugmentation and domestication(Jo et al. 2022 ; Wang et al. 2023 ); addition of various support materials such as activated carbon and magnetite (Li et al. 2023 ); and provision of trace elements and use of blowdown processes (Meng et al. 2020 ; Pedizzi et al. 2017 ). However, few articles have discussed and summarised the mechanism of ammonia inhibition in the AD process of nitrogenous organic wastes at the microbial level. Fundamentally, the AD process is a multi-stage, multi-level biochemical process that is mainly influenced by microorganisms, which are the core of the AD system(Li et al. 2017 ). It has been found that certain microorganisms are resistant to ammonia nitrogen inhibition during AD. However, coherent and targeted regulatory mechanisms to alleviate ammonia nitrogen inhibition remain elusive due to the complexity and variability of substrate properties, microbial sources and reaction conditions. To address ammonia inhibition and ensure digestive system stability, it is imperative to understand the extent of ammonia inhibition under various conditions, investigate the mechanisms and patterns of ammonia inhibition, and develop potential future regulatory strategies (Qian et al. 2017 ).

Based on this, this paper firstly describes the ammonia inhibition under different temperature, pH and reactor conditions. And the study of process intensification to implement ammonia inhibition mitigation in AD systems is described in detail. In addition, since the digestion process is mainly dominated by microorganisms, this paper focuses on analysing the causes and patterns of ammonia inhibition in AD from a microbial perspective. Finally, this paper summarises the current strategies and measures for mitigating ammonia inhibition in AD of nitrogenous organic wastes and looks forward to future research directions. This review aims to provide theoretical guidance for mitigating ammonia inhibition in AD.Fig.  1 describes the structure of this review.

Technology Roadmap

Inhibitory effect of ammonia nitrogen on AD process under different conditions

Although ammonia nitrogen promotes the growth of microorganisms at certain concentrations, it can exceed a threshold during substrate degradation and become toxic to microorganisms. Specifically, Anaerobic microorganisms are favorable to AD at ammonia concentrations of 50 ~ 200 mg/L, experience no antagonistic effects at 200 ~ 1000 mg/L, and are inhibited at 1500 ~ 3000 mg/L, especially in high pH anaerobic systems. Moreover, When ammonia nitrogen exceeds 3000 mg/L, microorganisms are inhibited to varying degrees in the AD process under any pH condition (Sung et al. 2003; Procházka et al. 2012b ). However, differences in temperature, reactor configuration, and the ammonia nitrogen inhibition levels tolerated by microbial communities in different systems make it impossible to accurately define thresholds. Table 1 lists the extent of ammonia nitrogen inhibition by each type of substrate under different conditions (Alsouleman,K 2019 ).

Different reactor types

Conventional AD systems are mainly categorized into single-phase and two-phase systems. In single-phase AD systems, all four AD steps occur concurrently within one reactor, while in two-phase AD systems, the acidification and methanization phases are separated into two tandem reactors (Ren et al. 2018 ; Shen et al. 2013 ), thus providing suitable conditions for the survival of acid-producing bacteria and methanogenic archaea. However Single-phase reactors lead to an increase in system loading because each reaction occurs in the same reactor. The rapid degradation of nitrogen-containing organic matter in a short period results in a swift increase in ammonia nitrogen content, which inhibits the activity of methanogenic bacteria and affects subsequent reactions (Bouallagui et al. 2009 ). For the same reactor, different feeding methods result in varying resistance to ammonia inhibition. For instance, Tian et al. ( 2017 ) evaluated three reactors (batch, fed-batch, and continuous) operating at medium (37 °C) and high (55 °C) temperatures and found that the batch-fed reactor had twice the free ammonia concentration of the batch reactor and that the continuously stirred reactor was inhibited at lower ammonia levels. In contrast, The two-phase reactor has the advantage of buffering the load in the first stage, allowing a more stable feed rate into the second stage for methane production. Ding et al. ( 2021 ) investigated the feasibility of a two-stage system to digest high-solids food waste as the sole feedstock in long-term operation. Compared to a single-stage system, the two-stage system had a 33.3% increase in food waste load, an 18.2% increase in energy yield, and was more resistant to ammonia nitrogen inhibition. However, the increase in system load can also lead to instability in the two-phase system. Ganesh et al. ( 2014a ) conducted a comparative study between single-phase and two-phase digestion of fruit and vegetable wastes and found that the two-phase system showed instability with lower methane and energy yields when the system load reached 7.0 kg VS/m 3 d. Since high concentrations of ammonia nitrogen can inhibit the digestion system and limit its organic load, future research should focus on reactor design to increase the organic load and avoid ammonia nitrogen inhibition (Nasr et al. 2012 ; Shen et al. 2013 ; Christou et al. 2021 ; Adghim et al. 2022 ). Figure  2 depicts the suppression of ammonia nitrogen under different conditions.

Suppression of ammonia nitrogen under different conditions

Different pH

The pH of an anaerobic fermentation system affects both microbial activity and ammonia nitrogen concentration. Under normal reactor operation, if the digested substrate is mainly composed of proteins, the pH of the digestion reactor is generally high. However, When the system pH is elevated, the transition of ammonia nitrogen to free state NH 3 will further affect the activities of anaerobic microorganisms, thus causing the accumulation of volatile fatty acids (VFAs) (Zhang et al. 2018 ; Park et al. 2018 ). At pH 6.5–8.5, the free ammonia content in the system increases by 3–18 times with a pH increase of 0.6–1.3. Consequently, after the accumulation of VFAs exceeds the buffer threshold, the system's pH will decrease significantly, resulting in system destabilization (Tian et al. 2019 ). For example, Ho et al. ( 2012 ) increased the biogas production of the system from 200 mL/L at pH 8.3 to 680 mL/L at pH 6.5 by adjusting the pH of the AD reactor feed, a 2.4-fold increase. Therefore, controlling the system pH is key to alleviating ammonia and nitrogen inhibition and maintaining the smooth operation of AD.

Different temperatures

Temperature is a significant factor affecting the ammonia threshold of the digestion system, as it isdirectly related to the microbial growth rate and free ammonia concentration in the digestion system (Ye et al. 2022 ; Liu et al. 2024 ). Medium and high temperature digestion each have their own advantages and disadvantages. Specifically, medium-temperature AD is cost-effective, has slow ammonia nitrogen accumulation, and higher biogas purity, but the biogas production rate is slower, and the tolerance limit for ammonia nitrogen is lower than that of high temperature digestion. Additionally, it also cannot effectively kill pathogens in the digestive system. High-temperature digestion is faster and more productive due to more complete degradation of raw materials, and the high temperature can effectively kill pathogens in the system, which is conducive to the secondary utilization of digestate. However, the methane content of the gas produced is lower, and ammonia nitrogen accumulates faster, leading to inhibition. Kim et al. ( 2011 ) found that the degree of protein destruction was higher under thermophilic conditions, and ammonia nitrogen content was higher in thermophilic phases due to protein degradation at increased organic loading rates (OLR). Furthermore, when the temperature increases, it enhances microbial metabolism, and the free ammonia content in the system rises consequently, increasing the ammonia nitrogen content in the system (Massé. et al. 2014 ; Angelidaki and Ahring 1993 ). For high ammonia loading digesters, the low-temperature AD process tends to have less ammonia inhibition and is found to be more stable than high/moderate temperatures. High-temperature digestion (operating temperature: 50 °C ~ 55 °C) is more susceptible to ammonia inhibition than moderate temperature digestion (operating temperature: 35 °C ~ 40 °C), leading to an unstable digestion system (Montecchio et al. 2017 ). Li et al. ( 2022 ) investigated the effects of bio-reinforcement on ammonia nitrogen in the digestive system at moderate and high temperatures using sludge as the substrate to explore the mitigation of ammonia inhibition by bio-augmentation. The results showed that methane production decreased by about 21% and 28% under medium and high temperature conditions, respectively, and thermophilic microorganisms responded more strongly to ammonia inhibition.

Microbial domestication

Different inoculated microorganisms have varying levels of tolerance to ammonia nitrogen, and microorganisms domesticated with high concentrations of ammonia nitrogen can improve their resistance to it. Studies have shown (Yenigün and Demirel 2013 ; Christou et al. 2021 ) that domestication of the microbial community in AD systems by progressively increasing the ammonia levels can increase the community's tolerance to ammonia. Specifically, inoculation with undomesticated microorganisms completely inhibited the digestion process when the system TAN concentration reached1700 ~ 1800 mg/L, while inoculation with domesticated microorganisms increased the inhibition threshold of TAN concentration to 5000 mg/L. Corresponding to a FAN concentration of 256 mg/L, the acid production process remained stable, indicating that the digester could still operate stably under low methane production conditions. However, Complete inhibition was observed when the TAN concentration reached 6700 mg/L. The effectiveness of biofortification is significantly influenced by the microbial composition of consortia. Wang et al. ( 2023 ) obtained two microbial consortia (syntrophic microbial consortium, MC, and hydrogenotrophic methanogen consortium, SS) by pure culture domestication and applied them to a nitrogen-enriched AD system (TAN concentration > 8 g/L). The results indicated that AD performance was restored within 21 days for the MC treatment and 83 days for the SS treatment. Although domestication of microorganisms is an effective method for resisting ammonia inhibition, it should be noted that domestication at high ammonia concentrations may cause irreversible damage to the microbial community structure (Nie et al. 2015 ; Zhang et al. 2022 ; Poirier et al. 2017 ).

To summarize, in the practical application of AD, two-phase reactors stand out due to their strong buffering capacity. Nevertheless, when the system load continuously increases, two-phase reactors can be inhibited. In engineering applications, the system load can be equalized by choosing an intermittent feeding method to ensure stable reactor operation. The selection of temperature and pH should focus on the appropriate range for microorganisms in the digestive system; Specifically, medium and high temperatures enhance microbial activity, thereby increasing the free ammonia concentration in the system, which leads to higher ammonia–nitrogen concentrations. Furthermore, changes in pH indicate variations in ammonia nitrogen and volatile acid concentrations in the system. Therefore, to prevent ammonia nitrogen inhibition, pH adjustment should be carried out based on low-temperature digestion. To further enhance the system's tolerance to ammonia nitrogen, inoculation with microorganisms that have been domesticated with high ammonia nitrogen concentrations can be considered. Within a certain range, as the ammonia nitrogen concentration in the system gradually increases,microorganisms can adapt to higher ammonia nitrogen environments, thus resisting ammonia nitrogen inhibition.

Ammonia Stress Mechanism

High ammonia nitrogen concentrations are an important factor contributing to the instability of AD. The bacterial flora is closely related to the operational efficiency and methane production rate of AD. The system includes hydrolysis-acidification bacteria, hydrogen-producing acetogens, acetotrophic methanogenic archaea, and hydrogenotrophic methanogenic archaea (Yang et al. 2018 ; Tian et al. 2018b ). Specifically, high ammonia concentrations affect the structure of the bacterial population in the AD system, thereby reducing the efficiency of AD. For instance, it has been demonstrated that the microbial community within the AD system responds to high concentrations of ammonia nitrogen, with methanogens being more sensitive to ammonia stress than hydrolysis-acidification bacteria and hydrogen-producing acetogens. Under nitrogen stress, the pathway of methane production is altered, and the dominant community in the system shifts from acetotrophic methanogenic archaea to hydrogenotrophic methanogenic archaea (Wang et al. 2022 ). Figure  3 shows the mechanism of ammonia inhibition in the AD system.

Mechanism of ammonia inhibition in AD system

Effect of ammonia on VFAs accumulation in AD systems

When the anaerobic system is destabilized by ammonia inhibition, both inhibition of acid secretion and the accumulation of large amounts of short-chain fatty acids, such as propionic acid and butyric acid, are often observed. However, the inhibitory effect of high nitrogen stress on acetogenic bacteria is selective, affecting the overall abundance of acetogenic bacteria such as digestive Enterobacteriaceae of the genus Pelotomaculum, desulphurizing Enterobacteriaceae of the genus Desulfotomaculium, and acid-producing hydroxyacetic acid bacteria of the genus Pelotomaculum. High nitrogen stress also resulted in a reduction in the genera Syntrophomonas and Syntrophus, as well as the overall abundance of the phylum Ascomycetes. The relative abundance of Desulfovibrio, a phylum of Proteobacteria, has also decreased. According to the literature, propionate and butyrate are directly utilized by Desulfovibrio, which converts them into acetate (Chen et al. 2016 ). Therefore, high ammonia concentrations significantly reduce the abundance of propionate and butyrate oxidizing microorganisms and their accessory bacteria.

Changes in the efficiency of the AD process and microbial population dynamics in food waste were examined by Peng et al. ( 2018 ). The study found that higher ammonia nitrogen concentrations significantly reduced Methanosaeta species abundance and inhibited acetic acid metabolism in the AD system. The accumulation of acetic acid inhibits the degradation of other volatile fatty acids, such as propionic acid and valeric acid, leading to a complete disruption of the entire AD metabolic network and possibly the collapse of the AD reactor. Niu et al. ( 2015a ) found that high ammonia concentration increased the diversity of bacterial communities and enriched acid-producing bacteria. Furthermore, throughout the entire AD process, hydrogenotrophic methanogenic archaea predominated, and the lack of acetotrophic methanogenic archaea led to the accumulation of acetic acid and other volatile fatty acids. This accumulation resulted in a reduction in methane production and destabilization of the reactor. It is evident that hydrogenotrophic methanogenic archaea are more resistant to ammonia stress than acetotrophic methanogenic archaea, and blocking acetic acid metabolism is the main cause of AD system destabilization (Ziganshin et al. 2013 ). In addition, Among the microorganisms that metabolize acetic acid, Methanosaeta is the most sensitive to ammonia, with its activity inhibited when TAN exceeds 2000 mg/L. In contrast, Methanosarcina and syntrophic acetate-oxidizing bacteria (SAOB) are more tolerant to ammonia. Thus,the introduction of domesticated Methanosarcina and SAOB into the system can restore system stability.

Effects of ammonia nitrogen on the dominant bacterial species in the AD system

In recent years, many researchers have attempted to introduce ammonia–nitrogen interference into reactors to study the microbial community structure, dominant bacterial species, and metabolic functions of AD flora under nitrogen stress conditions. For example, Ruiz-Sánchez et al. ( 2018 ) studied bacteria and archaea in AD systems under ammonia stress. They assessed diversity and found that ammonia had different effects on microbial diversity in different groups and conflicting effects on microbial diversity for each metabolic function. By comparing differences in the number of dominant microorganisms in AD reaction systems operating at four ammonia concentrations, they found that the dominant acidifying hydrolysing bacteria were from the genera Sporocytophaga and Nitratalea in AD reaction systems with TAN < 3000 mg/L. Similarly, Buhlman et al. ( 2019 ) showed that the dominant methanogenic pathway shifted from acetotrophic methanogens to synthetic trophic acetate oxidative-hydrogenotrophic methanogens when ammonia nitrogen concentration increased to 6133–8366 mg/L (Wang et al. 2015 ; Lee et al. 2021 ). In addition, the results of Niu et al. ( 2015a ) showed that bacterial communities subjected to ammonia inhibition mainly exhibited resistant or redundant traits. During ammonia inhibition, the dominant bacterial species were replaced to ensure that the gas production efficiency of the anaerobic digestion (AD) system was restored.

Influence of ammonia nitrogen on the activity of intracellular enzymes of microorganisms

During the AD process, the biotransformation of organic substrates is facilitated by various enzymes within microbial cells, as illustrated in Fig.  3 . Recent studies have increasingly focused on the role of microbial enzymes during anaerobic fermentation under ammonia stress. Using integrated multi-omics analysis, Zhang et al. ( 2022 ) demonstrated that ammonia stress in the AD system significantly reduces the expression activity of methyl coenzyme M reductase in methanogenic filamentous bacteria, thereby inhibiting the conversion of acetate to methane (Yan et al. 2020 ). In addition, Ammonia also inhibits the methylmalonyl-CoA (MMC) pathway in Pelotomaculum by suppressing the expression of succinyl coenzyme A synthetase, leading to the inhibition of propionate oxidation. Acetic acid metabolism is particularly sensitive to ammonia stress in AD. High ammonia nitrogen concentrations inhibit the expression of methyl coenzyme M reductase in methanogenic filamentous bacteria, thereby inhibiting acetic acid metabolism. However, continuous ammonia stress shifts the dominant acetate-degrading microorganisms to methanotrophic octococci with higher ammonia tolerance. The microbial community can be continuously optimized to restore acetate metabolism through the acetate-methane (AM) pathway, facilitated by enzymes such as acetic acid kinase, phosphoacetyltransferase, and deaminase (Poirier et al. 2016 ).

Under ammonia stress, propionic acid accumulates in the system, significantly reducing the rate of methane production. The abundance of propionate-oxidizing bacteria (SPOB) decreases, along with the expression of methane-related enzymes that degrade propionate, indicating that propionate metabolism is highly inhibited and more sensitive to ammonia stress. Therefore, SPOBs are crucial in influencing the function of the AD system under ammonia stress. They inhibit propionate metabolism by suppressing the expression of succinyl coenzyme A synthetase and the conversion of methylmalonyl coenzyme A. Wang et al. ( 2023 ) found that the accumulation of short-chain fatty acids, such as propionic acid, affects the activity of methanogenic bacteria, indirectly leading to system destabilization. Excess free ammonia reduces the number and activity of filamentous methanogenic bacteria of the genus Methanosaeta, inhibiting acetate metabolism and leading to reactor destabilization. Excess long-chain fatty acids (LCFAs) in the system create a synergistic inhibitory effect with ammonia. The relative abundance of Petrimonas and Paraclostridium species decreases, suggesting that high ammonia concentrations inhibit the β-oxidation of LCFAs (Wu et al. 2019 ). The abundance of enzymes such as acetate kinase, phosphopyruvate acetyltransferase, pyruvate synthase, phosphopyruvate hydratase, phosphoglycerate dehydrogenase, and glycine hydroxymethyltransferase, which are associated with acetic acid dehydroxylation, is significantly reduced. This suggests that high concentrations of nitrogen and ammonium primarily inhibit the oxidation reaction step of methane under synergistic inhibition conditions (Capson-Tojo et al. 2020 ; Peng et al. 2023b ; Yu et al. 2021 ).

Effect of ammonia on microbial cell morphology

The effect of free ammonia on AD performance was investigated by Calli et al ( 2005 ).They found that the cluster structure of Methanosarcina Methanoctococcus spp. was significantly decomposed at free ammonia concentrations greater than 700 mg/L. Furthermore, scanning electron microscope observations revealed obvious wrinkles, deformations, and cracks on the surface of the cells, indicating the destruction of cellular integrity (Park et al. 2018 ). In contrast, cells in the blank control group were intact in shape, tightly packed, and had smooth surfaces. The breakdown of cellular integrity leads to the loss of protective functions, which in turn results in cell damage, lysis, and death (Yan et al. 2019 ). Therefore, this study suggests that the effect of high concentrations of ammonia nitrogen on microbial cell activity and morphological structure is a crucial factor in ammonia inhibition. Different species of methanogenic bacteria exhibit varying tolerance to ammonia nitrogen, likely due to differences in cell morphology. For instance, filamentous cells with a larger specific surface area, characteristic of acetotrophic methanogenic archaea of the genus Methanosaeta, allow free ammonia to diffuse more easily into the cell. On the other hand, Methanosarcina and some species of hydrogenotrophic methanogenic archaea can form cell clusters under high ammonia stress, creating ecological niches in the centers of these clusters that help resist ammonia toxicity.

Effect of ammonia nitrogen on lipid molecules of microbial cells

The cell membrane is the main route for the exchange of substances between the cell and its environment and is crucial for maintaining growth and proper function. During the AD process, organic substrates generally need to be transported into the cell by crossing the cell membrane to metabolize substances (Linda-M et al. 2001 ). In recent years, researchers have shown interest in the effects of high ammonia nitrogen exposure on the key properties of microbial cell membranes. For example, Liu et al. ( 2023 ) showed that the permeability of the acetotrophic methanogenic archaea cell membrane increased significantly under nitrogen stress, exhibiting significant depolarization of the membrane potential, as shown in Fig.  4 . Furthermore, fluorescence polarization detection was conducted, revealing that the fluorescence polarization of cells in the AD system under high concentrations of ammonium nitrogen was significantly higher than in the control group (Tian et al. 2018a ; Astals et al. 2021 ). These results indicate that high concentrations of ammonium nitrogen cause a significant decrease in cell membrane fluidity.

cell membrane transport under nitrogen stress

Controlling strategy

During the AD process, approximately 33–80% of nitrogenous organic matter, such as urea, proteins, amino acids, and nucleic acids, are hydrolyzed and fermented, releasing ammonia and nitrogen as end products. Ammonia inhibits the normal metabolic functions of anaerobic microorganisms by disrupting intracellular pH/proton and potassium (K + ) ion balances, exacerbating cellular energy depletion, and inhibiting the activities of specific enzymes associated with methanogenic metabolism. Furthermore, due to the heightened sensitivity of methanogenic bacteria to ammonia, it leads to the accumulation of volatile fatty acids, thereby exacerbating the deterioration of the AD process. Strategies to mitigate ammonia inhibition by adjusting operating parameters (e.g., temperature, pH, and carbon to nitrogen ratio) and employing physicochemical methods (e.g., dilution, precipitation, air stripping, membrane separation, and ion exchange) have been extensively studied and reviewed. (Xu et al. 2022 ) Table  2 lists several measures to mitigate ammonia inhibition in the AD process.

Adjustment of the C/N ratio

The adjustment of the carbon to nitrogen (C/N) ratio is considered a crucial measure in mitigating the inhibition caused by ammonia nitrogen during the AD of organic wastes. When the C/N ratio is too low, it can lead to the accumulation of ammonia nitrogen within the system, potentially inhibiting AD microorganisms (Capson-Tojo et al. 2020 ; Yang et al. 2022 ). Conversely, a fermentation feedstock with an excessively high C/N ratio may result in an inadequate nitrogen source within the system, leading to an underutilized carbon source. The combined AD of various organic wastes is recognized for its ability to enhance waste utilization efficiency and reduce the need for multiple treatment facilities, thereby resulting in cost savings (Peng et al. 2022 ). Moreover, it is acknowledged that this process aids in improving the stability of the digestion procedure by increasing the C/N ratio of the feedstock, effectively mitigating the effects of ammonia nitrogen inhibition. In a study conducted by Wang et al. ( 2022 ), it was observed that when kitchen waste and food waste were co-digested at a mass ratio of 2:1, there was a significant increase in the gas production rate and methane content compared to the AD of kitchen waste alone. Specifically, at an organic loading rate (OLR) of about 120 kg·d -1 , the average volumetric mean biogas production rates for the AD and co-digestion of the two substrates were measured at 2.02, 0.75, and 2.3 m 3 ·m -3 ·d -1 , respectively. Similarly, the average methane content in the produced biogas was recorded at 38.4%, 21.2%, and 63.8% for the AD of kitchen waste alone and the co-digestion of the two substrates, respectively (Mahdy et al. 2020 ). Furthermore, Beniche et al. ( 2021 ) observed promising outcomes from the co-digestion of food waste combined with leaves and stems of kale and cauliflower at a C/N ratio of 45. The resultant mixed substrate exhibited high biodegradability, reaching 98%. This co-digestion process yielded a methane production of 475 mL STP CH 4 /g VS, both of which displayed enhancements compared to the performance achieved through sole AD.

Selection of adapted microorganisms

Microbial domestication is a pivotal strategy in alleviating ammonia nitrogen inhibition within waste digestion systems. This approach involves the deliberate cultivation or introduction of microbial flora capable of tolerating elevated ammonia nitrogen concentrations, thereby significantly enhancing the system's ability to manage ammonia nitrogen effectively. An essential phase in the domestication process is the screening and cultivation of microorganisms resilient to high ammonia nitrogen concentrations (Chen et al. 2018 ). This is typically achieved by subjecting the microbial flora to gradually increasing levels of ammonia nitrogen. Jo et al. ( 2022 ) demonstrated the enhancement of methane production rates within the system, increasing from 154.6 ± 9.9 mL/g COD to 269.6 ± 3.6 mL/g COD through microbial domestication. This domestication led to observable alterations in both bacterial and archaeal populations. Notably, the transition of archaeal populations from Methanobacterium spp. to Methanosaeta spp. and Methanosarcina spp. occurred concurrently throughout the domestication process (Carballa et al. 2015 ; Peng et al. 2023c ). Wang et al.( 2023 ) applied two microbial communities (MC and SS) through domestication to a nitrogen-enriched AD system and found that the MC and SS treatments restored AD performance within 21 and 83 days, respectively. Analysis of the 13 C isotope indicated that both MC and SS enhanced the hydrogenotrophic pathway.

Ammonia removal

The accumulation of ammonia nitrogen can significantly impede the efficiency of AD and potentially cause process failure. Ameliorating ammonia nitrogen inhibition can be accomplished through several methods, including the addition of auxiliary materials such as clay, zeolite, and guano, as well as utilizing membrane reaction contactors, incorporating trace elements, and employing the blow-off method. For instance, the guano stone method involves leveraging magnesium and phosphorus within guano to create insoluble magnesium ammonium phosphate precipitation (Ye et al. 2024 ; Zhuo et al. 2018 ). This process effectively removes phosphorus and aids in denitrification, thereby mitigating ammonia nitrogen accumulation. Li et al. ( 2022 ) investigated the impact of guano stone precipitation in removing ammonia nitrogen from the anaerobic fermentation process of chicken manure. Their study revealed a significant reduction in the ammonia nitrogen concentration within the test group reactor, decreasing from 2,937 mg/L to 1,466 mg/L. Consequently, the average methane production improved by 18%, increasing to 0.39 L/g compared to the control group's 0.33 L/g. Furthermore, the addition of trace element Fe demonstrated an antagonistic effect on ammonia nitrogen, with this effect notably intensifying as the ammonia nitrogen concentration increased. Meng et al. ( 2020 ) explored the use of zero valent iron (ZVI, 150 µm) to enhance methanogenic capacity. The introduction of ZVI at 160 mM notably amplified cumulative methane production by 22.2% and further reduced the high-solid anaerobic digestion (HSAD) duration by 50.6%. Additionally, the blow-off method, which transfers ammonia nitrogen from the liquid phase to the gas phase, emerged as an efficient physical nitrogen removal process with low investment costs, relatively straightforward equipment requirements, and simple operational procedures. Pedizzi et al. ( 2017 ) implemented an air sidestream vapor stripping process to reduce ammonia nitrogen concentration. Their study demonstrated a successful reduction of ammonia nitrogen concentration from 2.4 ± 0.1 g N-TAN L -1 to 1.1 ± 0.1 g N-TAN L -1 , without compromising process stability. Furthermore, they achieved a reduction from 4.5 ± 2.0 g N-TAN L -1 to 2.0 ± 0.1 g N-TAN L -1 , highlighting the effectiveness of their approach. Similarly, Zhuang et al. ( 2018 ) demonstrated that the addition of magnetite nanoparticles resulted in a 36–58% increase in methane production compared to the control group. Additionally, it was observed that magnetite nanoparticles had a minimal impact on TAN concentration, suggesting that conductive materials have a relatively minor effect on ammonia levels, yet they diminish the inhibitory effects of ammonia nitrogen (Ngo et al. 2023 ; Provolo et al. 2017 ; Zhao et al. 2019 ).

limitations and future directions of research

Based on the above, the anaerobic digestion (AD) process is a complex biochemical system grounded in thermodynamic principles and driven by microorganisms that work synergistically through commensal linkages to maintain system stability. However, these microorganisms are highly sensitive to environmental fluctuations, which, given the complexity of the substrates and the stochastic nature of AD operating conditions, could adversely affect the performance of AD facilities. Consequently, there has been significant scientific interest in exploring whether the addition of microorganisms with specific biodegradative capabilities—a bioaugmentation strategy involving the introduction of specialized microbial functional groups into inhibited AD systems—can mitigate toxicity under high ammonia concentrations and enhance reactor performance. For instance, Methanoculleus and Methanosarcina have been identified as effective bioaugmentation agents for counteracting ammonia inhibition. Research has shown that adding Methanoculleus to an AD system utilizing municipal solid waste as a substrate can increase methane production by 21% (Wang et al. 2023 ). Additionally, the introduction of bacteria-rich bioadditives, such as propionic acid and butyric acid-degrading bacteria, has been found to accelerate the conversion of volatile fatty acids (VFAs) to methane. This acceleration is largely attributed to the interactions within the complex bacterial community, which help reduce hydrogen partial pressure (Li et al. 2022 ).

Although the bioaugmentation strategy of cultivating pure strains can be effective in enhancing the digestive performance of anaerobic reactors under ammonia stress, it is accompanied by some risks, i.e., it is difficult for a single archaea to colonise and rebuild the microbial community in systems suppressed by high ammonia and nitrogen concentrations (Wang et al. 2023 ). In addition, the cost and technical requirements (sterile environment, culture media) associated with the cultivation of pure strains are realities that have to be taken into account. Therefore, biofortification strategies using mixed microbial consortia (consisting of microorganisms that can tolerate inhibitory factors) are a more effective alternative in order to better fit the host microbial community as well as to improve the tolerance of the system to ammonia stress. For example, Yang et al. ( 2019 ) combined Methanobrevibacter and syntrophic acetate oxidizing bacteria (SAOB) (Syntrophaceticu schinkii) as a microbial consortium and methane yield was improved by 71%. However, whether these selected microbial consortia are stably able to function in high-ammonia inhibition systems needs to be confirmed by extensive experiments. For instance, Westerholm et al. ( 2012 ) combined some SAOBs (Clostridium ultunense sp,Tepidanaerobacter acetatoxydans, and Syntrophaceticus schinkii) with ahydrogenotrophic methanogen (Methanoculleus) to construct a microbial consortium as a biological additive but the digestion performance was not improved after adding the microbial consortium. Interestingly, microbial symbionts obtained through purposeful domestication are more closely related yet better adapted than artificial microbial symbionts. Consequently, they may yield superior results in enhancing digestive performance in AD systems with high TAN concentrations (Wang et al. 2023 ). However, there remains a knowledge gap regarding the effectiveness and potential mechanisms of microbial symbionts acquired through purposeful domestication as bioadditives for alleviating ammonia inhibition. Specifically, the potential mechanisms of microbial symbionts obtained through purposeful domestication in mitigating ammonia inhibition may be more complex than those of individual archaea or artificially assembled microbial symbionts, and the roles of individual members within a microbial symbiont in mitigating ammonia inhibition are still unknown. Much future research is needed. In addition, a reliable set of mathematical models to predict the efficiency of different biofortification would provide a more efficient solution for selecting a mixed microbial consortium that is tolerant to ammonia stress and thus improve the digestive performance of the AD system.

AD stands as a pivotal biological treatment method that effectively converts organic wastes into valuable biogas while simultaneously reducing waste volume. Nevertheless, the accumulation of ammonia nitrogen within this process can trigger ammonia nitrogen inhibition, thereby restricting the efficiency and stability of the digestion process. To mitigate this inhibition, various measures have been implemented. These include the adjustment of the C/N ratio, pH regulation, addition of VFAs, utilization of ammonia nitrogen adsorbents, adoption of ammonia nitrogen removal processes, alongside gas stripping and blow-off techniques. In essence, these collective measures collectively contribute to the reduction of ammonia–nitrogen concentrations and serve to alleviate the inhibition effects within the AD system. Adjusting the C/N ratio through co-elimination methods aids in diminishing the accumulation of ammonia nitrogen. pH regulation and the utilization of ammonia nitrogen adsorbents assist in preserving a neutral or alkaline environment, thereby reducing the concentration of free ammonia nitrogen. Additionally, vapor stripping and blow-off techniques work to facilitate the release of ammonia nitrogen by enhancing the rate of gas–liquid mass transfer. These approaches collectively enhance the efficiency and stability of the AD system.

In the future, there is potential for further exploration of novel methods and advanced technologies aimed at more effectively mitigating ammonia nitrogen inhibition. Particularly, the investigation of innovative microbial domestication strategies holds promise in enhancing microbial adaptation within high ammonia–nitrogen environments. Moreover, delving into the intricate interrelationships between ammonia nitrogen inhibition and various other waste treatment parameters can significantly contribute to the refinement and optimization of waste digestion systems. Ultimately, such endeavors are poised to significantly enhance the feasibility of mitigating ammonia nitrogen inhibition, thus fostering improvements in the efficiency and stability of the AD process.

Abbreviations

Municipal solid waste

Organic waste

• Anaerobic digestion

Total ammonia nitrogen

Free ammonia

Organic loading rates

Syntrophic microbial consortium

Hydrogenotrophic methanogen consortium

Syntrophic acetate-oxidizing bacteria

Wood-Ljungdahl pathway

Methylmalonyl-CoA

Acetate-methane

Propionate-oxidizing bacteria

Long-chain fatty acids

Volatile fatty acids

Carbon to nitrogen

Organic loading rate

Zero valent iron

High-solid anaerobic digestion

Syntrophic acetate oxidizing bacteria

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Yang, J., Zhang, J., Du, X. et al. Ammonia inhibition in anaerobic digestion of organic waste: a review. Int. J. Environ. Sci. Technol. (2024). https://doi.org/10.1007/s13762-024-06029-1

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Selective laser sintering of polymers: process parameters, machine learning approaches, and future directions.

1. Introduction

2. principle of sls, 3. applications of sls, 4. materials fabricated by sls, 5. challenges associated with fabricating polymers using sls technology [ 26 , 33 , 38 , 39 ], 6. sls parameters, 6.1. laser power, 6.2. scanning speed, 6.3. layer thickness, 6.4. hatch spacing, 6.5. preheating temperature, 6.6. powder particle size distribution, 6.7. part bed temperature (t b ), 6.8. thermal distribution, 6.9. powder morphology, 7. porosity in sls parts, 8. machine learning ml for sls, 8.1. overview, 8.2. ml-based monitoring methods.

Click here to enlarge figure

8.3. Process Optimization

8.4. defect detections, 9. conclusions.

• The quality and properties of SLS-produced parts are heavily influenced by numerous process parameters. Key factors include laser power, scanning speed, layer thickness, hatch spacing, preheating temperatures, powder particle size distribution, and part bed temperatures. Careful optimization of these parameters is crucial for achieving desired part qualities such as density, strength, and surface finish.
• Laser power has a direct impact on density and hardness, with both properties increasing as laser power increases. Scan spacing is a crucial parameter that significantly impacts both the density and hardness of the printed parts. Experimental findings reveal that an increase in scan spacing leads to a decrease in both density and hardness. Consequently, to achieve optimal performance in these metrics, it is recommended to use a low scan spacing value, such as 0.1 mm.
• The relationship between bed temperature and hardness is linear, with hardness continuously increasing as bed temperatures increase. However, the effect of bed temperature on density is more complex, with density initially increasing and then decreasing as bed temperatures further increase.
• Scan count has a positive correlation with density, with higher scan counts resulting in increased density. However, the effect of scan count on hardness is dependent on bed temperature. At lower scan counts, increasing bed temperatures lead to increased hardness, while at higher scan counts (e.g., 2), the trend reverses, with hardness decreasing as bed temperatures increase.
• By leveraging the power of ML and optimizing the process parameters, SLS has the potential to revolutionize the manufacturing industry, enabling the production of high-quality, customized parts with improved efficiency and sustainability.
• ML techniques have demonstrated high accuracy in defect detection for SLS processes. For instance, the VGG16 convolutional neural network model achieved impressive metrics for powder bed defect classification, including accuracy (0.958), precision (0.939), recall (0.980), F1-score (0.959), and AUC value (0.982) [ 133 ].
• The challenges in applying ML to SLS are significant and quantifiable. Data availability is a major issue, with many ML studies on SLS relying on limited datasets, often ranging from a few hundred to a few thousand data points. This highlights the need for larger, more diverse datasets to improve model accuracy and generalizability.
• The development of high-performance polymers and composite materials.
• Focusing on increasing print speed and building larger parts or assemblies.
• The integration of SLS with other manufacturing technologies, such as robotic arms and automation systems, to enhance its capabilities and applications.

Author Contributions

Data availability statement, acknowledgments, conflicts of interest.

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Yehia, H.M.; Hamada, A.; Sebaey, T.A.; Abd-Elaziem, W. Selective Laser Sintering of Polymers: Process Parameters, Machine Learning Approaches, and Future Directions. J. Manuf. Mater. Process. 2024 , 8 , 197. https://doi.org/10.3390/jmmp8050197

Yehia HM, Hamada A, Sebaey TA, Abd-Elaziem W. Selective Laser Sintering of Polymers: Process Parameters, Machine Learning Approaches, and Future Directions. Journal of Manufacturing and Materials Processing . 2024; 8(5):197. https://doi.org/10.3390/jmmp8050197

Yehia, Hossam M., Atef Hamada, Tamer A. Sebaey, and Walaa Abd-Elaziem. 2024. "Selective Laser Sintering of Polymers: Process Parameters, Machine Learning Approaches, and Future Directions" Journal of Manufacturing and Materials Processing 8, no. 5: 197. https://doi.org/10.3390/jmmp8050197

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