Should reference numbers be located after the punctuation?

Question

I saw in a research article that reference numbers were located after the punctuation. E.g. in the screenshot below, there are a few reference numbers that I underlined in red: they are located after , and .. Is that correct?

Answer 1

According to The Chicago Manual of Style^†, section 14.21, this is the normal way to do it:

A note number should generally be placed at the end of a sentence or at the end of a clause. The number normally follows a quotation (whether it is run into the text or set as an extract). Relative to other punctuation, the number follows any punctuation mark except for the dash, which it precedes. (emphasis added)

In my experience (which is mostly from reading linguistics papers), this is the usual practice. I decided to check my memory, so I opened ten papers at random on my hard drive by different authors. I found that nine followed this practice, while the remaining paper placed the superscript reference number before any punctuation. So it seems (at least from a sample of linguistics papers) that this practice isn't followed universally, but I'd nonetheless recommend you follow common practice both for aesthetic reasons and to avoid distracting the reader.

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^† Thanks to Jason Patterson for pointing this out in the comments section.

Answer 2

This is a matter of citation style, and different style guides may prescribe different formats. All the ones I know of specify that reference numbers come after any punctuation.

When citing sources in Wikipedia, its manual of style says:

... citation markers are normally placed after adjacent punctuation such as periods (full stops) and commas. ... Note also that no space is added before the citation marker.

On a related page Wikipedia gives more detail:

The ref tags should immediately follow the text to which the footnote applies, with no intervening space (except possibly a hair space, generated by {{hsp}}). Any punctuation (see exceptions below) must precede the ref tags. Adjacent ref tags should have no space between them. This applies to all ref tags, including both explanatory notes and citation footnotes.

...

Exceptions: Ref tags are placed before dashes, not after. Where a footnote applies only to material within parentheses, the ref tags belong just before the closing parenthesis.

Note The above rules apply only to formatting citations within Wikipedia articles on the English-language Wikipedia site, and do not prescribe the format for any other use, although the style is similar to that used elsewhere.

Answer 3

I don't know about footnotes or references numbers, but I do know that parenthetical citations are indeed always placed after punctuation. (Like This p. 42) This would lead me to believe that reference numbers are also placed after punctuation.

Edit: Hmm, seems I don't remember my writing classes as well as I thought; only long quotations are cited after punctuation, short quotations are cited immediately.

Source: https://owl.english.purdue.edu/owl/resource/747/03/