Worldcat is a collaborative effort produced by OCLC (Online Computer Library Center) and supported and used by 72,000 libraries in countries around the world. It's principal aim is to create a union catalog wherein a user can search and discover books and other holdings from among any of the member libraries.

With over 300 million holdings, the breadth of Worldcat is astounding and usually contains pointers to records that are truly rare or unique among library holdings.

When a search on Biblio results in no copies for sale, a link is provided to re-create that same search among OCLC libraries using the Worldcat interface.