Optimum number of references for a research paper – and how to achieve that number

There is no universal standard or rule for the number of references that should appear in a research paper. The number of references depends on several factors, chiefly the study discipline and specific topic, the article type and the target journal’s preferences.

Reference number by study discipline and niche

• Discipline: The average number of references per article has been observed to be higher for social sciences, physics and ecology than for medical sciences.
• Niche: If you are working on a highly researched topic, you might end up having a lot of references. However, within a broad field, a niche or narrow subdiscipline or a very new and original idea, say ‘indigenous languages of the Mascarene Islands’, might have very few pre-existing studies, so you may not have very many studies to cite. 

Reference number by article type

• Reviews: Review articles, systematic reviews and meta-analyses tend to have long reference lists because, by definition, such studies critically assess the data from existing studies.
• Reports: Case reports or other types of short reports cite very few references because the primary focus is the authors’ current findings.
• Original: An original article would have a reference number between that of review articles and short reports.

Reference number by journal 

Some journals might have restrictions on the maximum number of references, further contingent on article type and total word count. For example, references might be capped at three (e.g. for a ‘Disease Note’ article in the Journal of Plant Pathology) or could be as high as 100 (e.g. for reviews in PLOS Pathogens). In Nature, original articles typically have 30–50 references.

Our recommendation: Always consult the journal’s author guidelines for specific limits, if any. Where not specified, skim recently published articles in that journal for a rough estimate.

Tips to help you optimise your reference list

Not every paper you might have read during the literature review needs to be included. To strike the right balance between too many or too few, keep the following key points in mind when compiling your references.

1. Scan academic journals in your field 

Study the trends of journals in your discipline, with a focus on the article type you have in mind. Get a rough idea of the number of references typically listed by checking how many references other authors have included in their papers. 

2. Strike a balance between retaining and removing

Are some of your statements supported by a long list of references? Try to sift through the noise and retain only those that strongly support the statement and are not repetitive. For example, among several studies that have used the same genetic analysis approach in different species, choose the one most relevant to your study.

‘Responsible citation’ requires that you consult and understand the content of a paper before choosing to cite it, rather than including it just because others have cited it. In short…

• Retain references if they are truly relevant to your research.
• Remove references if you have not read the cited article fully.

Summary

There is no standard number of references for an article. However, the following pointers should help you work towards an optimal number.

• Keep track of general trends for specific article types by examining the most recent relevant publications.
• When a limit is prescribed, treat it as sacrosanct; do not exceed it.
• When no limit is indicated, cite an adequate number required for your paper.

With practice, you will learn to strike the perfect balance of not too many and not too few!

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