I feel a bit awkward, but my question is this: Someone asked questions on Mathoverflow and I gave answers. The whole thing was not very deep and I could provide rather standard examples to show whether something is true or not (I do not want to be more specific now).

I noticed on the arxiv a paper by this same person containing my answers but giving no reference to mathoverflow. What should I do in this case?

I would drop it, because there were no significant ideas in my answers, and anyone with some thinking and search in the literature could come to the same conclusion. But it is more a question about mathoverflow: it is somehow a misuse of the site. It is not about me, but about the fact that someone asked for help in this site, got this help but is not acknowledging it.

ADDED: My problem is solved now due to the helpful and cordial intervention of the moderators. Thank you for your diplomatic way.

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    $\begingroup$ You might think of a way to bring to their attention this thread. $\endgroup$ Commented Apr 16, 2014 at 13:42
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    $\begingroup$ I noticed something similar too a few months back where the answer of another user (not me) was used substantially in the paper. What was used was not too hard, and I felt that the user who answered would probably not want credit (and perhaps had even been asked by the author of the paper -- I obviously don't know the facts). Again legally the paper was ok, but ethically seemed questionable to me. Francois Dorais below suggests how MO answers should be treated: Is that position officially recorded somewhere? $\endgroup$
    – Lucia
    Commented Apr 16, 2014 at 15:57
  • $\begingroup$ I had a similar experience, actually. The user did acknowledge other people who answered his questions, though. $\endgroup$
    – Asaf Karagila Mod
    Commented Apr 16, 2014 at 16:36
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    $\begingroup$ @Lucia: It's not a "position", "policy" or anything of the sort. Posting on MathOverflow is a mode of communication and all forms of communication between professionals need to be handled professionally. $\endgroup$ Commented Apr 16, 2014 at 17:19
  • $\begingroup$ Tread carefully. I am in a situation where I pointed out some results on MathOverflow to some in the hopes of collaboration; the result is consistent with their ignoring me, developing the material independently, publicizing it without acknowledgment, and privately maintaining that MathOverflow is not appropriate as a reference. Hopefully MathOverflow Inc. (LLC?) will decide what their preference is on handling such issues. Dropping it may be a good legal if not a good ethical option. Gerhard "There Are Some Other Options" Paseman, 2014.04.17 $\endgroup$ Commented Apr 17, 2014 at 20:41

2 Answers 2


MathOverflow is a means of communication between professional mathematicians. By standard professional ethics, these should be properly acknowledged in the same way that similar exchanges (informal discussions, email exchanges, circulated notes, published papers, as appropriate) are normally acknowledged, to the extent possible.

Note that we are currently working on means to ensure permanence of the MathOverflow database, which will facilitate proper and stable referencing of MathOverflow posts.

If you would like to ask how to properly react to a potential breach of professional ethics by a colleague, please ask on Academia.SE since it's tangential here and you may get even better responses there.

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    $\begingroup$ Thank you. I do not believe there is a breach here in the juristic sense. $\endgroup$ Commented Apr 16, 2014 at 14:25

Let me discuss your question from the other point of view: someone who finds himself in the position of using things he learnt on math overflow. I was in this case for a recent article I wrote. Here is what I put in the "thanks" part: "Je tiens à remercier en tout premier lieu la communauté du forum mathoverflow. J’y ai posé durant la rédaction de cet article de nombreuses questions, dont les réponses (ainsi parfois que les réponses à des questions posées par d’autres) m’ont donné des références, des idées, parfois mêmes des preuves, que j’ai utilisées (dans ce dernier cas, les preuves sont attribuées nommément ci-dessous à leurs auteurs sur mathoverflow)"

So I thanked collectively the whole MO community for its help, and nominally the people who gave me an argument of some sort (as opposed as just a reference). In doing so, I had sometimes to make a choice. Some results were useful to me but I felt that they were completely trivial for the answerer, and I was not sure I would not anger him in citing his name in relations with that triviality. Another delicate choice was with one answerer with was anonymous. I left a comment under his/her answer where I required him to contact me if he/she pleased, so that I could thank him/her nominally, but the comment was left unanswered (perhaps unseen). Finally I did not include the result I learnt from him/her for my paper (for unrelated reasons).

Basically, I think the rule of thumb for quoting a result you learnt on MO is exactly the same as for your proverbial colleague down the hall who answered a question of you. You mention or thank him/her if you think his/her contribution is significant, and there a considerable room for interpretation here.

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    $\begingroup$ I think there is a significant difference between the proverbial colleague and MathOverflow: the former (and likely you) are not recording the conversation you had, whereas MathOverflow does record things. You and your readers thus have something that they can access and independently evaluate. How much you reveal to the reader is also interpretable, but not as broadly. I recommend at least listing the questions that were useful, if not also the answers. Perhaps someone might see something you missed. Gerhard "MathOverflow Is Too An Entity" Paseman, 2014.04.28 $\endgroup$ Commented Apr 28, 2014 at 16:51
  • $\begingroup$ Thank you. My question was about cases when something is almost verbatim taken from MO. My concern is, as @GerhardPaseman mentions, that in some cases when writing a paper you use copyrighted material. This you are free to use but common professional etiquette is to mention the source, even if only vaguely as general thanks. $\endgroup$ Commented Apr 28, 2014 at 18:07
  • $\begingroup$ Gehrard, good point. Each time I thank someone for an argument he gave me on MO, I will also give the question number so that the reader can easily see for himself. $\endgroup$
    – Joël
    Commented Apr 30, 2014 at 15:06

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