National and Union Catalogs

Center for Research Libraries (UB is a member) About CRL
COPAC - a merged online catalog of 24 university research libraries in the UK and Ireland
European Library Portal for 43 national libraries of Europe
Karlsruhe Virtual Catalogue - Access to books and serials in library and book trade catalogs worldwide
Lib-Web-Cats - Access to catalogs of more than 4,000 libraries world-wide
LibDex, a worldwide directory of library catalogs (sorted by country)
Libweb - Library homepages worldwide
Library of Congress
National Libraries (by country)
National Library of Medicine Catalog
Open WorldCat - Records of library-owned materials in OCLC's WorldCat database