refer-bib-files

refer-bib-files is a variable defined in `refer.el'.
Its value is

dir

• Automatically becomes buffer-local when set.

Documentation:
List of \.bib files to search for references,
or one of the following special values:
nil = prompt for \.bib file (if visiting a \.bib file, use it as default)
auto = read \.bib file names from appropriate command in buffer (see
`refer-bib-files-regexp') unless the buffer's mode is `bibtex-mode',
in which case only the buffer is searched
dir = use all \.bib files in directories referenced by `refer-bib-directory'.

If a specified file doesn't exist and has no extension, a \.bib extension
is automatically tried.

If `refer-bib-files' is nil, auto or dir, it is setq'd to the appropriate
list of files when it is first used if `refer-cache-bib-files' is t. If
`refer-cache-bib-files' is nil, the list of \.bib files to use is re-read
each time it is needed.

You can customize this variable.