In our post about the recommended style of citing on chemistry.se we state:

The highest principle should always be: Give credit.

I like it how many answers substantiate their explanations with external references. Giving the citation correctly is especially important when (block) quoting from the original.

It is also very important when using images from external sites, that require a certain way of attribution. (Please always check that you have the permission to redistribute images.) In some cases the image is used and the source is indicated by including a link. For example like this:

(source) [In this case both links are the same, because they are from our own site.]

Sometimes this is sufficient, but more often this is not. When using images from stack exchange, everybody is expected (read: required) to follow some basic rules. In that spirit the above mentioned source should have been:

Source: paracresol, chemistry.stackexchange.com.

Any other use would be a violation of copyright and could give rise to removal. That is especially bad when the question/answer becomes void. It is only fair to follow our own rules. When using public domain images it is nice to indicate that they are. For example:

chemistry teacher public domain (public domain image)

I do always assume for an image on our site, that the author of the post is also the creator of the image if it is not stated otherwise. I admit that I might have done that incorrectly in the past sometimes, but I tried to fix these instances.

Obviously that doesn't stop at images.
Whenever I come across a post that is linking to an external source and when I have the time I try to include the actual citation or amend the source to follow copyright guidelines. (If I don't have time to do that, I usually only leave a link). Except for one time it was either completely ignored or welcomed. The following should serve as short example, what I find insufficient:

Steinmetz and Grimme investigated the performance of density functionals for bond activations with catalysts of these metals. They find:

The PBE0 hybrid functional, together with our atom-pairwise dispersion correction (D3), shows the best performance for the complete set followed by PW6B95-D3, the corresponding double-hybrid functional PWPB95-D3, and B3LYP-D3.

While it gives the authors names and links back to the resource pdf (in this case the publisher pdf), if the journal decides to change that, or the journal changes publisher, or is sold/closed down, you might not be able to find the resource again. In general I would at least see this as a somewhat questionable scientific method. [In this special case I used an open access resource, so there will probably be an accessible copy elsewhere.]
This becomes more dramatically worse when it is not the link to the publisher resource, but to a different source (like an institute homepage, preprint, etc., it does not have to be illegal). This is quite neatly demonstrated by the related meta question: Policy on linking to papers? The question linked there suffers from link rot via the exact process described in it. This wouldn't matter much if the citation has been given, or at least a (more) stable link would have been inserted. In the above example I would have included the following, after replacing the link with a citation marker.

  1. M. Steinmetz, S. Grimme, ChemistryOpen 2013, 2, 115–124.

This uses the double fallback as you have the written out citation, which you can find via a search engine, and it is linking via the DOI, which we can assume to be around for quite some time.

All this leads me to basically to the title question:

Should we enforce including actual citations?

And with enforce I mean (actively) encourage to include citations, or insert them ourselves as edits from a (not-yet-dead) link to the sources?

  • 2
    $\begingroup$ The issue has came up often where a real paper has been cited, the OP comments that they're unable to access it, and then someone else comments with "you can find it (illegally) on sci-xxx.xxx". $\endgroup$
    – NotEvans.
    Commented Jan 16, 2017 at 18:14
  • 1
    $\begingroup$ Note that link rot has already happened on this site in several cases, for example when IUPAC moved Pure and Applied Chemistry from their own servers to de Gruyter. $\endgroup$
    – user7951
    Commented Jan 17, 2017 at 10:48

2 Answers 2


I propose to formulate a community guideline that clarifies how references should be given in questions and answers, permits all users to make any corresponding changes, and encourages users to do so:

Preliminary remarks

Any post must not include any content that infringes any copyright of another party (see terms of service).

Every post (question or answer) must include the proper attribution of any contributions of others (from an external source or another post on Stack Exchange) by appropriate referencing. Posting the work of others with no indication that it is not your own is considered plagiarism, is frowned on by our community, and may result in the post being down-voted or deleted (see How to reference material written by others).

These contributions may include texts, images, or data. However, simple structural formulas are ineligible for copyright and therefore in the public domain. No attribution is required for data if only a typical or rounded value is used, values are widely available from various sources, no particular source is required to support the used value, and the exact value is not relevant for the answer (e.g. “the boiling point of ethanol is about 78 °C”). Nevertheless, if in doubt, the post should include proper attribution.

The recommended (preferred but not necessarily required) form of attribution for external sources is as follows:

Where possible, the attribution should include a reference in human-readable form and a link to the source.

Trasatti, S.; Petrii, O. A. Real surface area measurements in electrochemistry. Pure Appl. Chem. 1991, 63 (5), 711–734.

  • The recommended format for the reference is described in the meta post What is the recommended style of citing on chemistry.se?.

    However, authors of questions or answers may use any other suitable format. Sufficient information must be provided so that the source can be identified and located. Periodical references shall include the author names, abbreviated journal title, year of publication, volume number (if any), and initial page of cited article (the complete span is preferred). Book references shall include the names of the authors or editors, book title, publisher, city of publication, and year of publication.

  • Methods to format links are described in How do I format my posts using Markdown or HTML?.

    Where possible, the link should be a digital object identifier (DOI) link, which is guaranteed never to change.


    If the corresponding source is behind a paywall, it may be useful to also add an alternative link to any free source.

  • Some online encyclopedias are often updated with new content; therefore, it may be useful to use a permanent link, which leads to the text as it was at the time. Wikipedia offers a “Cite this page” tool that automatically creates references in various styles, for example: https://en.wikipedia.org/w/index.php?title=Special:CiteThisPage&page=Benzene&id=751982820 (see also Citing Wikipedia), which can be easily adapted.

    Benzene. Wikipedia, The Free Encyclopedia [Online]; Posted November 28, 2016. https://en.wikipedia.org/w/index.php?title=Benzene&oldid=751982820 (accessed Nov 28, 2016).

    However, note that Wikipedia is not considered a reliable source.

  • Authors of questions or answers may use any other format for the references or incomplete references; such course of action is deprecated but not prohibited. Bad references are better than no reference at all, and they should be neither deleted without replacement nor flagged.

  • Editors may improve any reference that is incomplete or not in accordance with the recommended format so that it conforms with the recommendations, and are encouraged to do so. Editors (including the original author) shall not change any reference that is already in accordance with the recommended format to any other format.

If you find a broken link in a reference, please try to fix the link yourself, leave a comment for the author of the post, or flag the post for moderator attention.


Should we enforce rigorous standards for citations?

Yes, probably. Chasing citations is a much larger proportional burden to the community, though, since the sources must be searched out anew; inclusion by the OP is much easier, since they've already tracked them down at the time of writing the post.

Is it realistic to expect people to properly cite sources, even in the presence of specific guidelines?

Sadly, probably not. Better guidelines will probably move the needle a few percent, but I can't imagine they'll lead to a sea change.

Do we have the ability to induce/coerce compliance with a citation policy?

I don't think so - I think it'd require the SO overlords to implement some sort of change to the site feature set. One possibility would be a (reversible) community vote for "improper citations" that, e.g.: (a) negatively impacts reputation; (b) provides a visible stigma, say an "anti-badge" of sorts; (c) negatively impacts site privileges (e.g., blocked from asking/answering if 'improper citation' counts are above some threshold); or some other tangible consequence.

In sum: It's A Really Good Thing™ if we can make it happen, but unfortunately I fear it's A Really Challenging Thing To Actually Make Happen™.

  • 1
    $\begingroup$ I am not arguing for chasing down every citation. I just wanted to spell out why I think it is important to include them and propose that anyone should be able to spell out a citation if that wasn't done by the OP. I don't think we need guidelines for this at all. Since we are a science site, I think that everybody will sooner or later learn how to cite correctly and leading by example is a good way to induce that. There are already ways to voice your opinion on bad citation manners: Comment, edit, down-vote. There really does not have to be any more. $\endgroup$ Commented Jan 25, 2017 at 5:02

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