In physics, it seems to be common practice to reuse your own introductory material, verbatim, multiple times in online lecture notes and conference preceedings, and a final time in a journal article. In most instances, it isn't indicated that the material was previously posted elsewhere, and the original documents may not be referenced at all.

This surprised me. During my undergraduate studies, we were given strict warnings about plagiarism, including self-plagiarism. I understand that authors are reluctant to reuse introductory material once it has been published in journal articles because it would violate copyright.

Is this practice really above board? and does it differ from other fields? If so, why?

1 Answer 1


Research ethics: At least around mathematics, self-plagiarism is defined much more narrowly than plagiarism. Essentially, in order to self-plagiarize, you have to write a paper that contains no new results whatsoever (compared to your older work); just having some overlap is not a problem. Verbatim self-repetition is not regarded as problematic (although it will make people think you are lazy or a bad writer) as long as it does not pretend to be new material. Repeating research papers in lecture notes or textbooks is not considered wrong.

Some even take the point of view that publishing the same result many times (first sloppily, then better, then really well) is legitimate; see Rota's "Publish the Same Result Several Times" advice. (Note: This advice is probably controversial, particularly these days, when there are few "obscure" journals, and when there is no reason to publish a crappy draft when you can just post it on the arXiv. But a second publication that subsumes and improves on a previous paper won't usually be considered improper. Also, you can publish a draft of ongoing research in conference proceedings and then re-publish it in a proper paper; that's what conferences are for.)

Copyright: There is, as always, a noticeable disconnect between what is legally required and what is actually done. In terms of the former, there may well be problems. In terms of the latter, you shouldn't worry. Unless you copy and republish a whole book, no one will sue you. (And even annoyances such as takedown requests to your university tend to be rare -- and don't always correlate with actual breaches of copyright.) Academics disregard copyright six ways from Sunday; if they suddenly started to care, research and teaching would probably slow down to a grind for a year or so until the most important sources are rewritten and published as open content. You should almost always ask yourself "what will the reader think", not "what will Elsevier think", at least if you are planning to get hired by academics rather than by Elsevier :)

  • But what if the academics who are hiring you are as stuck up as some of those commercial publishers? Do you have an actual source that says that verbatim self-copying of a little portion that is not the key part of the paper is actually considered okay in mathematics?
    – user21820
    Commented Feb 21, 2019 at 15:21
  • @user21820: I have no sources on it, but I've just seen it happen so often that it cannot possibly matter. Academics (even editors) usually are not deeply enough involved with publishers to care. Commented Feb 21, 2019 at 15:25
  • Hmm are you saying that (usually) editors of mathematical journals don't even use software to detect plagiarism, or that they do but disregard it if the copied part is not put up as a major contribution in both papers?
    – user21820
    Commented Feb 21, 2019 at 15:31
  • @user21820: I have not seen editors use plagiarism detection software so far -- though I would probably not know if they did, and either way it's likely that they will in the future. But almost anyone in a serious journal would know to take a critical look at the results produced by such software rather than just consider a numerical value it spits out. Commented Feb 21, 2019 at 15:36
  • I see, yea I would expect that. But who knows, if a publisher makes copyright demands down the road...
    – user21820
    Commented Feb 21, 2019 at 16:11

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