I am peer-reviewing an article "A" and I found something interesting. The authors use a mathematical lemma (which is just an inequality) for which they cite article "B". I have used this inequality before for many years, but noticed that "B" is an article from 2019, so evidently this inequality wasn't discovered/derived for the first time in "B". I was curious so I managed to obtain this article "B" and noticed that they use the same inequality by citing article "C". A similar thing happens in "C" by citing "D", and so on until we get to "F". Notice that in this whole "citation tower" no new information is added: the mathematical lemma remained essentially the same.

Moreover, some of the same authors appear in some of the works A,B,...,F but not in all and not consecutively. However, an author of "A" is also an author of "F". Finally, in "F" (which is an article from 2011) the authors provide the mathematical lemma, and provide a proof for it. However, I have seen other works in the literature which uses this result even before 2011, and actually I can track it all the way until I reach a famous (but OLD) book "Z" which provides the same inequality but not necessarily using the same notation.

Do you think this "citation tower" (is there another name for this practice?) is a bad enough practice to point it out in my review? Up to now I am considering the following things to do with my review (regarding this issue only):

  1. Do nothing. The authors are using a result from the literature by appropriately citing it.

  2. Just suggest them to cite "F" instead of "B".

  3. Suggest them to cite "Z" instead of "B".

However, since an author of "A" is also an author of "F", under the assumption that this citation tower is indeed a bad practice, and that the result was given in "F" as if it was discovered there even when this result was known many years before, there is a fourth option:

  1. Point them out this issue describing it as a bad practice in order to help preventing it in the future. Moreover, I was thinking in asking the reviewers to cite "F" and adding a note in the final manuscript saying that the result was shown in "F" using modern notation, but it was known to be true since "Z".

EDIT AFTER SUBMITTING MY REVIEW: It is very hard to chose a correct answer, since I don't believe there is a single one. There are very nice answers here, but I will mark as correct the one that mostly resembles what I did at the end.

  • 6
    It could be that the authors cite B instead of F because it presents the lemma in a better way in some kind (notation, context, ability to read it out-of-context, ...). But there is no harm in pointing it out.
    – user151413
    Commented Jan 4, 2021 at 13:44
  • 3
    I agree. However, B and F are both works in the same context. Moreover, both present the lemma in exactly the same way (almost same text, maybe one or two words different, and same notation). I've been thinking about this, and I dont see any advantage of citing B instead of F. Commented Jan 4, 2021 at 14:24
  • 4
    Are there other references to B? Commented Jan 4, 2021 at 19:34
  • 6
    I think the question of user3067860 was if B would be in the reference list of the reviewable paper even if it wasn't used for this particular lemma?
    – Džuris
    Commented Jan 5, 2021 at 12:50
  • 8
    Ah... interesting point, that would be a reason to cite B instead of Z or F indeed. But no, B is not mentioned elsewhere Commented Jan 5, 2021 at 14:50

7 Answers 7


You're assuming the reasons for the citations. Maybe they want more citations to their own work. Maybe they forgot. Maybe they don't know any better.

Your job as a reviewer is to comment on the scientific article. Ask the authors to explain their citations. One way to write a comment along the lines of:

The authors cite A that provides proof for X. However, it's not clear why A is chosen in preference to F or Z. I suggest that the authors add something like: "The proof appeared first in Z, but was rewritten in modern notation in F, and an instructive example of its application to similar problems in given in A."—if that's indeed the case, as I suspect.

This way you are informing the authors that there are citations missing, in your opinion, telling them which ones are missing, not blaming anyone for doing anything, and giving them a concrete example on how to justify their choices.

  • 3
    Thanks! I am currently more inclined to write something like what you suggested in my recommendation. My assumption for the reason of the citation was due to the fact that an author of A is also an author of F. But it is perfectly reasonable that they simply forgot. No reason to blame anyone, but point out my observations on this issue. Commented Jan 5, 2021 at 14:57
  • Gimelist, 'there's no particular reason we chose B. we don't wanna change it to F because we're lazy. is this going to be a problem?' your response is? cc @FeedbackLooper
    – BCLC
    Commented Oct 20, 2021 at 16:47
  • @BCLC you are the reviewer, not the editor. Tell the editor what you think, and let them make the call.
    – Gimelist
    Commented Oct 20, 2021 at 21:43

I think this requires some nuance. You seem to suggest that citing the earliest usage is preferable, and it might be. But it might also be the case that each subsequent usage adds something to the context. That is to say that the citation appears in the chain for some particular use and the reader of the current paper might find it useful to explore that history. Each of those citations is surrounded by context that can be useful.

If you always cite only the earliest usage, then the reader has no hints about the overall usage context of that thing cited. And the current author might be inviting the exploration.

Of course, it might also be that the author(s) considers the lemma to be a minor point and has used the citation they found without chasing the chain back themself, not seeing any need for it in the current context.

Overdone, in mathematics, we just always cite Euclid.

So, I don't think citing a later, rather than an earlier paper is a bad practice necessarily, but could be in a particular instance.

You can always note the other citations in your review and point to the earliest one without making any specific recommendation.

  • 2
    Good points. Sure I know that citing the earliest work is far from the best strategy in all cases. This context part makes a lot of sense. I was suspicious that the authors just wanted to increase citations for other works. But maybe I was misjudging this whole situation, that why I posted the question, looking for a different opinion. So your answer is very valuable to me and I will reconsider what I will do with my review. Commented Jan 4, 2021 at 11:39
  • 3
    Perhaps they should cite both B and Z (B for its context, Z because its older)? Commented Jan 4, 2021 at 23:39
  • 2
    -1 No point in writing a review without recommendations. Commented Jan 5, 2021 at 2:10
  • 20
    -1. If you state a lemma that has appeared earlier, you should always mention the earliest source you are aware of. Giving the credit to the original creator of an idea is a fundamental part of scientific culture. So there is nuance to whether you should cite the other sources, but you must cite Z. Commented Jan 5, 2021 at 10:58
  • 3
    @DavidKetcheson, I agree completely for important results, but for minor lemmas, that seems impractical -- not to mention that crediting the earliest printed source you can find today isn't necessarily giving credit to the creator of the idea. I'm sure I can find plenty of things presented without attribution in old textbooks (which is what OP's Z is) that were nevertheless known since ancient Greek times, so I don't think there's much value in hunting down the oldest book surviving that shows it, unless that one claims it's an original result.
    – Nate S.
    Commented Jan 6, 2021 at 20:39

In your case, the author of A that was also an author of F should have cited F instead of B. It's unlikely that that author forgot the reference F; it's more likely that they wanted more citations for B.

I recommend that you go with your option 4. Tell them to cite Z and F.

  • 4
    I'd add that there is no reason to tell the authors not to cite B-E if they are relevant. Commented Jan 5, 2021 at 2:12
  • 1
    Maybe the paper is mainly building on B and so they cite B by default and instead avoid citing F to avoid reference padding.
    – Džuris
    Commented Jan 5, 2021 at 12:52
  • I don't write papers like this, but with stuff I do write I like to add a "not referenced but related information that might be useful" section. It might also help to give a short paragraph explaining why it's useful.
    – Ben
    Commented Jan 5, 2021 at 13:41
  • 1
    I've had more than one occasion where someone discussed one of my papers with my that I had completely forgotten writing. While citing F might be better, B is more likely to be freshly in mind, and also might well be getting cited for other reasons (it seems possible this paper is building on B). While the citation should be fixed, I wouldn't assume this was intentional citation gathering. Commented Jan 6, 2021 at 12:10

Vaguely calling something “bad practice” is, well, bad practice. You should be able to articulate precisely what’s bad about it. And it sounds to me like what’s bad about it is that it is misleading: it misleads the reader into thinking this lemma is new when it obviously has a long history, and that the credit for it is due to a different set of authors than the people it’s really due to.

With that in mind, I think everyone can agree that misleading readers is indeed “bad practice” and should be avoided, especially when it’s easy to do so. So it seems to me completely appropriate to ask in your review that the authors of “A” should cite the book “Z” either in place of, or in addition to, citing any subset of the papers “B” through “F”. And you can also suggest that they optionally add a brief comment outlining the history of the lemma and pointing out any relevant issues of notation as appropriate, depending on which of these sources they end up citing exactly.


It seems no answer so far makes the following point: if you're reading a paper and decide to follow up a reference for a mathematical statement, it's probably because you want to know the proof. Therefore, from the reader's perspective (the perspective that matters), "F" is the most appropriate citation, since it gives the proof in modern notation.

Therefore, if I was the reviewer, I would recommend that the authors cite paper "F" in addition to "B" (or instead of it, but there's no reason to tell them not to cite "B" unless it's really not relevant). I would also mention "Z" and suggest they mention it, but I'd put less stress on that, since it's likely to be less useful for the reader than "F". Essentially, I think your option 4 is the best one.

  • 1
    I suspect many don't really see the citations as serving that purpose, but rather just to avoid the appearance that they made up a fact without justification.
    – Barmar
    Commented Jan 5, 2021 at 15:17
  • 1
    " it's probably because you want to know the proof. " <- Not necessarily; you may be more interested in the context in which it was used before.
    – einpoklum
    Commented Jan 6, 2021 at 13:06

There are several purposes of citations. The primary one is providing support for a claim; if you don't include a proof of a claim, but cite a paper that does, then that proof is incorporated by reference into your paper. If B doesn't actually include the proof, but rather cites C, then citing B doesn't serve the purpose of incorporating a proof into A. Not citing the original paper makes tracking down the proof more difficult, if not impossible. It can also make it look like there are several papers supporting a claim, when in fact there is only one original source. For instance, someone publishes Paper A claiming that they did a study and found that foobars often commit mopery. Paper B then claims foobars often commit mopery and cites Paper A. Paper C and D then claim that foobars often commit mopery and cites Paper B. Then Paper E claims that foobars often commit mopery and cites Paper C and Paper F claims that foobars often commit mopery and cites Paper D. Now someone comes along and writes a newspaper article and says "There's overwhelming evidence that foobars often commit mopery! Here are six different papers that show this." And if someone tries to factcheck the article, it's going to take them awhile to track down all the citations and realize that there's only one paper that is actually original research. It's also possible for the chain of citations to actually be circular. See citogenesis.

It's a common phenomenon on Snopes when trying to track down a claim to find this sort of citation chain, and often the claim is distorted in each link of the chain, with the final result being quite different from the original, and often what looks like several different sources are actually from one ultimate source. It also has proliferated on the internet; an article or post will talk about something and post a link, but rather than going to the original source, this link goes to another article or post, and so on.

The second purpose is to give credit. The primary credit gives to the earliest paper, and so that should be the primary citation. If another paper expanded on that, and/or brought it to your attention, then it may merit a citation as well, but it should be in addition, not instead of, the other citation.

The third purpose is to give further reading to those who are interested in learning more. This is where a citation to B is most justified, but a citation to F and/or Z may also be useful.


You did already follow all the chain so you could judge if the references are adequate or not. Did they point to the context specific usage of the lemma, or are there to gives a theoretical ground?

In one case it could be fine to cite late literature, in the other they should have traced things to the root.

If I would be the referee, I would consider just the above without thinking of bad or good practice. Eventually, asking to add the first, proof giving paper.

  • I agree. The context and usage is basically the same in all references B,...,F, they use the inequality for almost the same purpose, and for a similar application. Commented Jan 5, 2021 at 10:52

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