This is a follow on to Are citations in abstracts considered bad style? It is unclear to me how to format the citation. Are citations in the abstract covered by any style guide (APA, MLA, Chicago, AMS, etc) and how do they depend on if a numeric system is being used versus an author-year type system?
I was not able to find any mention of references in the abstracts in APA, MLA, Chicago, ASA (both statistics and sociology). There is no indication of if they are allowed and if so, if new formatting is required. I have found a few style guides that do describe references in the abstract.
APS style says:
References cited in the abstract must also be found in the Reference List, where the complete information for the reference is provided. However, in the abstract, these references are not cited by their reference number alone. Instead, the following form of citation is used: the entire author list with initials (in roman); the journal name (in italics); and the volume, page numbers, and year (in roman). The article title is omitted for the sake of brevity.
which is pretty thin in regards to a citation style
IEEE style says:
Numbered reference citations are not allowed.
which might imply full text citations are allowed like APS, but it goes on to say
The abstract must be self-contained, without abbreviations, footnotes, or references. It should be a microcosm of the full article.
AMS style seems to be the most complete:
The abstract needs to be edited to remove or rewrite reference citations. Rewrite reference citations by placing the following information within brackets at the callout point. For journal article references, insert (in all lightface roman text) the journal abbreviation, volume, year, and page numbers, but not the article title. For book references, insert the title, publisher, location of publisher, and year. Only book titles appear in italics
it then gives three examples (article, book, and what looks like a book chapter).
I checked my copy of the Chicago Manual of Style, 16th edition, but I couldn't find any reference to this problem (I might overlooked it, though).
We had once to cite a paper in an abstract, because the results given there were central for our paper. The publisher put the reference inline, within parentheses, with the same format of the other references. That particular journal has a particularly short form for the references, and the inline citation read as:
(Author A, J. Abbrv., Vol. (Year) Start page)