You can find a book's call number in the online catalog. You will need your library card to do this. The circulation desk is near the entrance. It may be a reference to a text that has been quoted, or to some source that has been used as an authority. A single citation is sometimes called a reference.
Many databases are in the form of CD-ROMs.
The date stamped in the back of the book that reminds you when the book must be returned to the library. This can be used in two ways. The Library has indexes of this second type on many different subjects. See a Reference Librarian for advice. There usually is no charge for this service.