Function: reftex-citation

Make a citation using BibTeX database files.
After prompting for a regular expression, scans the buffers with
bibtex entries (taken from the \bibliography command) and offers the
matching entries for selection. The selected entry is formatted according
to `reftex-cite-format' and inserted into the buffer.

If NO-INSERT is non-nil, nothing is inserted, only the selected key returned.

FORMAT-KEY can be used to pre-select a citation format.

When called with a `C-u' prefix, prompt for optional arguments in
cite macros. When called with a numeric prefix, make that many
citations. When called with point inside the braces of a `\cite'
command, it will add another key, ignoring the value of

The regular expression uses an expanded syntax: && is interpreted as `and'.
Thus, `aaaa&&bbb' matches entries which contain both `aaaa' and `bbb'.
While entering the regexp, completion on knows citation keys is possible.
`=' is a good regular expression to match all entries in all files. (fn &optional NO-INSERT FORMAT-KEY)