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I was rather shocked when hearing in a conversation that journals sometimes have explicit limits on the number of references that can be included in one article. I understand that there are space concerns for print publications, and that word/page limits, as well as limits on the numbers of figures and tables are common. But placing limits on the number of references strike me as rather close to impinging on the integrity of the articles themselves (would anyone support a motion to limit the number of authors?).

Question: What are some reasons that have led journals to limit the number of references?

Clarification: I am not asking whether this is a good idea in general. (I think it is silly, but that's just my opinion.) I am not asking whether this can have some potentially good effect on the quality of scientific writing. I am specifically asking whether there was an official explanation ever issued on the part of the publishers explaining this rule, or whether there was some event (say, an abuse in the form of many gratuitous references or an observed trend for the average number of references to keep growing if not otherwise checked) or some strong personality (famous editor-in-chief X) that led to these kinds of policies being formulated.

For example, Applied Physics Letters has limits on number of words (with some conversion factor applied also to figures and tables), but (in my opinion, rightly) excludes the title, the author list, and the list of references from the limit.

For examples of journals (from various publishers) that have limits on number of references:

  • Nature "strictly enforces" a limit of 50 for articles and 30 for letters. (Science, I note, does not for research articles. For review articles the limit is 100.)
  • Earth and Planetary Science Letters limits to 50.
  • Blood "recommends" a limit of 100 references, though I don't know if this is a hard limit or not.
  • Journal of Clinical Ontology limits to 10 for "correspondences" and a "suggested limit" of 150 for "research articles".
  • Journal of Genetics (more reasonably, in my opinion), have different limits for different types of articles. But notably for research and review articles there are no limit to references: the reference number limit applies to shorter submissions such as correspondence, commentary, or "research notes".

Some additional information:

(TL;DR: Nature put in their current policy sometime between the years 1986 and 1988, with no reference limits prior. Did something happen in the 80s?)

I went down to the library and looked at the old issues of Nature (not because I want to single them out, but because the library happen to have all the issues since the 20s available on the stacks). After some binary search I've found that in December 1986 the instructions to the authors look like this (with no mention of limit to references)

Author Guideline 1986

and in October 1988 it became almost the same as present day (apologies for the flash... the lighting in the stacks wasn't good).

Author Guideline 1988

(I don't have the exact date of the switch, since only some of the issues in the library came from the original magazines; others came from bound reprints ordered from the publisher which stripped out pages like these. So in particular I found no "Guides to Authors" in the 1987 issues I had access to.)

Back in the 20s and 30s most of the items in Nature had no references whatsoever. By the 50s and 60s we start seeing articles more in the form of what we expect today, but the number of references are generally not too many. Even in the 70s and the 80s (before the change of rules) the majority of the articles do abide by the modern rules, with occasional exceptions.

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    would anyone support a motion to limit the number of authors? Yes – Cape Code Jun 24 '15 at 13:07
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    @JonCuster: "The journals that have decided on reference limits have done so with a conscious decision for a reason... From your comments below you do not see their side of it at all." That's why I asked the question. If you do see their side, educate me, please? – Willie Wong Jun 24 '15 at 13:27
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    In fact, if most authors never exceed 20 references, a limit of 30 references is a solution in search of a non-existent problem. I am inclined to believe the policy was instituted because there actually was once a problem. The question is: what was it? Was there actually an observed upward creep in the number of references before the policy was instituted? Was there a big scandal concerning gratuitous references? Was there a famous complaint about the decline of the state of scientific writing? – Willie Wong Jun 24 '15 at 13:44
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    @JonCuster: Throughout this whole discussion you have asserted that they have their reasons. I have never disputed that. I don't feel strongly about the fact that journals have reference limits. I have never run against them and probably never will. I do, however, feel strongly about your comments which entirely mischaracterize my question and my motives. I refuse to believe, based on your words and your words alone, that journals instituted this policy just to help us write better. I am more inclined to believe that the journals instituted this policy because of problems of ... – Willie Wong Jun 24 '15 at 15:36
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    ...gratuitous citations. But I have edited my question one hour ago to be extremely specific (in line with the Stack Exchange preference for factual answerable questions): if the worries are gratuitous citations, what led to this worry? I invite you to re-read my previous comment. // As an aside I found your comments highly demeaning, and I thank you to stick to the facts and stop casting aspersions based on imaginary intent. – Willie Wong Jun 24 '15 at 15:39
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Journals aim to publish an organized set of articles of some approximate length in an attractive format.

Journals set limits on the number of references to shape the form, format, and quality of the submitted articles.

This organization is a good thing, in terms of disseminating scientific information. Given the limited space of one article, there is definitely some appropriate range for the number of essential and useful references that relate to the presented work.

This is less restrictive that it might sound, as these rules set by the journal are seldom hard limits. If you have good reason to include a couple of extra references, you can usually work with the editor to get them included.

Another reason to include limits is to try to encourage authors to examine references more closely, and to be more selective in their choices of what to include. Just as many journals have rules against gratuitous figures and tables (e.g. all figs must be referenced in the text), these limits are meant to discourage gratuitous inclusion of references that are not directly related to the discussion in the manuscript.


In response to the expanded question: "What happened in the 80's?" ...

The Science Citation Index was launched in 1964. With its growth and success, and the addition of other field-specific indices, it became possible to compute statistical journal and author comparisons (e.g. Impact Factor). This concerted effort to index citations made being cited in the work of others more important, and the use of numerous citations became much more common. The benefits of these author and journal metrics were much lauded during the 70's and 80's, but people were also increasingly aware that this arrangement was vulnerable to abuse, i.e. gaming the system by inflating citations. SCI grew to become Web of Knowledge, then Web of Science and along the way (1992) it was acquired by a large media company and today it's run by Thomson-Reuters.

The question posed invites speculation; we can't know exactly what the owners and editors of the various scientific journals were thinking when they started implementing citation limits. However, I would hazard a guess that they realized gratuitous citations might be an issue, probably had a few bad apples, and decided that limits were a good idea to keep the quality of the submissions high.

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    Plenty of journals makes space recommendations without explicit mention of the number of references. For length considerations a simple "total word count" with references included can suffice. – Willie Wong Jun 24 '15 at 12:51
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    And whether references are "essential and useful" should be delegated to the referees, and not decided by a computer based on an arbitrary number. Indeed, if the intent is for the quality of the articles, such concerns about the references being "essential" can be both included in the instructions to the authors and the referees in lieu of a numeric count. – Willie Wong Jun 24 '15 at 12:52
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    @WillieWong : I certainly agree that referees and the editor should determine what should be included, but that doesn't preclude the application of some guidelines for the general form of an article. – dionys Jun 24 '15 at 12:55
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    @WillieWong Putting the onus on the referees to 'enforce a limit of references' is corralling cats after they've walked out the door. Setting out guidelines that (upon justified request can be excepted) guide the product before submission, seems a better way to manage the system. I'm not saying I agree with limits on references, but if there are going to be limits, guidance should be before submission and not after. – CGCampbell Jun 24 '15 at 17:12
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    @CGCampbell: guidance I agree with, but wording is important. It would be nice if instead just stating matter-of-factly that there is a reference limit, the instruction reads something like: "Please only include scientifically necessary references, typical research articles in this journal have between 10 and 40 citations, while typical letters have between 2 and 25." With the implication that if you are an "outlier", we will scrutinize it; and even if you are within the norm, you don't get carte blanche to fill up the reference section with crap. – Willie Wong Jun 25 '15 at 8:53
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In the dim past (40+ years ago?), people had no idea how often one was cited... so there was scant motivation to generate gratuitous citations of oneself by trading gratuitous citations of others. There was no "citation index", etc.

From even longer past, there has not been too much tradition of careful acknowledgement of prior art, especially not of competing art, and not of historical antecedents, whether well-known or obscure. That is, "scholarship" has rarely been relevant to publishability or enhanced status. So, no need to have substantial bibliographies, since as much would be ignored as possible.

Maybe time to air out the quotation from a very well-known mathematician, to the effect (and I think it was not a joke) that if one didn't read other peoples' papers, one would not have to ever cite them...

So, in mathematics, the current style has "evolved" to only citing things "logically necessary". Rather unhelpful even to fairly-expert readers, but helping the readers is not the main goal... >:-(

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    In my (perhaps idealistic) opinion, helping readers (and thereby writing a better article) should be the main goal. Inflated citation counts may have some short-term benefits in terms of impact factor, but relevant high-quality citations are actually quite important leads for connecting research. I'm plenty cynical about some of the practices I see in the literature, but really it's up to all of us who participate in peer-review and publishing to move these things in a positive direction if they are ever to improve. – dionys Feb 15 '16 at 13:15

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