I am currently a referee for a paper. One of the authors of the paper had written an earlier paper, which I will refer to as the "original paper," and the paper which I am now refereeing is an extension of the original paper, which I will refer to as the "extension paper."

I have found that large portions of the extension paper are copied from his original paper. In particular, a whole section of definitions is copied from his original paper; and some paragraphs in the introduction and literature review are copied wholesale or with slight modifications from the original paper.

Is it acceptable for an academic paper to copy paragraphs and even a section from an earlier paper by the same author?

My intuition suggests that it is acceptable to copy the definition section, with an acknowledgement that it came from the original paper, since definitions are standard. But it seems strange to me for the introduction and literature review to be too similar to the original paper.

  • I tend to agree with you. In my experience with empirical papers, it seems totally OK to copy/paste parts about the research methods (that happen to be identical to previous papers), but not OK to do that with sections where you describe the broader significance of your results or where you give a theoretical overview.
    – Ana
    Commented Nov 5, 2014 at 16:15
  • Possible duplicate of Attitudes towards self-plagiarism
    – ff524
    Commented Nov 5, 2014 at 16:42
  • 5
    It's okay to copy definitions, even from other people's papers, as long as you make the appropriate citations. Definitions are (and should be) standard. Commented Nov 5, 2014 at 20:22

3 Answers 3


The answer depends on the relationship between the papers, and I'm not sure which applies based on the information in your question. In computer science, at least, there are two general cases:

  • The extension paper is the "extended journal version" of a previously published short-form work such as a conference paper, workshop paper, or extended abstract. In this case, the rule of thumb is typically at least 30% new material. The extended paper will often contain large chunks verbatim, as it is expected to supersede the original paper, rather than existing as a separate work.

  • The extension paper is a separate work: in this case, extensive reuse of material is self-plagiarism. Two exceptions: first, related work, methods, and definitional material may often be reused as long as it is appropriate to do so---the material should be appropriately customized to fit the new environment. If the author would just be paraphrasing for the sake of paraphrasing, though, it's not necessary. Second, introductory material may be partially shared, though it should be more heavily customized for the new context.

In all cases except for minor reuse of related work material, the extension paper must declare a clear and explicit relationship with the prior paper.

Note that many other fields do not have the notion of a "journal version" and thus have much stricter standards.

  • 4
    +1 for the 30% new material rule and for "The extended paper will often contain large chunks verbatim, as it is expected to supersede the original paper"
    – Alexandros
    Commented Nov 5, 2014 at 17:53
  • 1
    I think there's another relationship worth mentioning, although it's not at issue in this particular question: I have seen cases where journal articles were republished with some revisions in an edited volume. Often these are not quite reprints because they may include a small amount of new analysis, or altered intro/conclusion to fit the theme of the volume, but the bulk of the paper may be lifted straight from the earlier publication. Also, the copying is usually acknolwedged with a note saying something like "an earlier version of this paper appeared in Journal X".
    – BrenBarn
    Commented Nov 6, 2014 at 3:43
  • @BrenBarn Good point... I've seen book chapters that way too on occasion.
    – jakebeal
    Commented Nov 6, 2014 at 4:09

Publishers have concerns about this from a couple of directions.

  1. Copyright. A publisher will generally not want to publish something without making sure that the copyright is clear. If you've previously published a paper and then recycle text from that earlier paper into the new paper you need to make sure that you have retained the copyright on the text. Chances are that if you published your previous paper with a main stream commercial publisher then you transferred the copyright to that publisher and don't have the right to publish the same text in a new paper.

  2. Originality. Most publishers have policies that say they only publish original research papers. It's an editorial decision whether the new paper has enough original content to qualify as original research. Reusing the text of mathematical definitions and standard theorems is a gray area where some publishers are willing to allow some text recycling. If this is done, it's critical that the original source be properly cited or better yet that the material be treated as a quotation from the original work.

Most publishers now use software to automatically check all submissions before they're sent out for review. If there's a concern about old fashioned plagiarism or recycling of text ("self plagiarism"), then this is often dealt with before the paper is even sent out for review.

As a referee, I would note the recycling of text from the previous paper and then review the current paper and consider whether the new work is sufficiently original to merit publication. It will ultimately be up to the publisher to decide whether they're willing to deal with any liability for copyright violation that results from the text recycling.

The Committee on Publication Ethics (COPE) has some useful guidelines on text recycling:


  • 1
    To be a bit more direct. Although it used to be common to recycle text from "methods" and "literature review" sections, most publishers now frown on this and it is becoming increasingly difficult to publish papers that reuse text in this way. Commented Nov 5, 2014 at 23:56

One thing to consider is to flag it up to the editor/publisher. Most review systems have a way to provide comments to the editor only (not the original author). This is a case where you can flag up and discuss these aspects of the paper. Of course if the paper actually does not contribute anything beyond the original paper (in the same words or new ones) you could reject the paper on those grounds.

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