refer-bib-files-regexp

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

"\\\\bibliography"

Documentation:
Regexp matching a bibliography file declaration.
The current buffer is expected to contain a line such as
\bibliography{file1,file2,file3}
which is read to set up `refer-bib-files'. The regexp must specify the command
(such as \bibliography) that is used to specify the list of bib files. The
command is expected to specify a file name, or a list of comma-separated file
names, within curly braces.
If a specified file doesn't exist and has no extension, a \.bib extension
is automatically tried.

You can customize this variable.