reftex-cite-format

reftex-cite-format is a variable defined in `reftex-vars.el'.
Its value is

default

Documentation:
The format of citations to be inserted into the buffer.
It can be a string or an alist or a symbol. In the simplest case this
is just the string "\cite{%l}", which is also the default. See the
definition of `reftex-cite-format-builtin' for more complex examples.

If `reftex-cite-format' is a string, it will be used as the format.
In the format, the following percent escapes will be expanded.

%l The BibTeX label of the citation.
%a List of author names, see also `reftex-cite-punctuation'.
%2a Like %a, but abbreviate more than 2 authors like Jones et al.
%A First author name only.
%e Works like %a, but on list of editor names. (%2e and %E work a well)

It is also possible to access all other BibTeX database fields:
%b booktitle %c chapter %d edition %h howpublished
%i institution %j journal %k key %m month
%n number %N note %o organization %p pages
%P first page %r address %s school %u publisher
%U url %t title %v volume %y year
%B booktitle, abbreviated %T title, abbreviated

Usually, only %l is needed. The other stuff is mainly for the echo area
display, and for (setq reftex-comment-citations t).

%< as a special operator kills punctuation and space around it after the
string has been formatted.

A pair of square brackets indicates an optional argument, and RefTeX
will prompt for the values of these arguments.

Beware that all this only works with BibTeX database files. When
citations are made from the \bibitems in an explicit thebibliography
environment, only %l is available.

If `reftex-cite-format' is an alist of characters and strings, the user
will be prompted for a character to select one of the possible format
strings.
In order to configure this variable, you can either set
`reftex-cite-format' directly yourself or set it to the SYMBOL of one of
the predefined styles. The predefined symbols are those which have an
association in the constant `reftex-cite-format-builtin'.
E.g.: (setq reftex-cite-format 'natbib)

You can customize this variable.