Refers to an entry in the bibliography associated with this document. In the current application, the content is interpreted as the key to an entry in a BibTeX database.
attribution, cite, code, dt, em, entry, foreign, kbd, line, p, px, quote, span, strong, verbatim
( #pcdata
)
citation |_(#PCDATA)
If this attribute is present, then the application should include a reference to this citation in the bibliography, but without actually referring to the entry at this position in the text.