citations - Is there such thing as too many references for one paper?

I'm currently reviewing a paper that has an uncommonly large number of references compared to the average number for that particular venue (more than 60 versus around 30). This is a regular paper, not a survey one, and although there does not seem to be wrong references, it feels like some are not really necessary, and the fact that one particular author is cited more than 15 times makes me worry that this paper is used to inflate the number of citations of that author (the submission is anonymous).

Should I mention this in my review, and try to examine which submissions are "abusive", or just let it go?

Answer

It's really a judgment call… some people consider that more references is good, because it gives the reader a wider perspective into the issue, and some people consider it a bad practice (in old times because it wasted paper, but nowadays mainly because it obscures the more valuable information inside a long wall of text).

I have, as a reviewer, sometimes asked authors to cut down on the number of references, so it is certainly an acceptable practice. Here are some factors you may consider when making the decision:

• Does each individual reference bring something to the paper, i.e. is used to back up a fact, idea, or to give credit for a specific (and relevant) new idea that it introduced?


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  Are references cited in block? I tend to consider it is very bad practice:

  
  

  
  

  A series of recent experiments have shown systematically that current human-powered aircrafts are not suitable for mass transportation [refs. 9–21]

  
  

  
  

  Each paper (or group of two or three papers, at the very most) should be used with regards to a specific point in the discussion.

  
  
  


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  Somewhat disguised form of the earlier: are long lists of claims and references justified? Sometimes many citations are used as “examples”, where a few would suffice.

  
  


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  Could some of the citations be replaced by one or two reviews on the topic?

  
  


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  Are the work cited really the seminal work on each topic/idea/experiment, or are there also less “worthy” works cited?

  
  

Finally, it is true that there are some unethical practices that can lead to inflated number of citations. Excessive self-citation is certainly one, but there are others. For example, some authors cite very widely papers from all groups in their field, even when it is not really warranted, in an effort to help their chances at peer review: the idea is that the reviewer is less likely to be harsh to a manuscript that cites 5 of her own papers.

And in conclusion, if you believe that self-citation was the motivation, there is nothing wrong with reporting your doubts to the editor.