Central catalogs allow you to search the resources of multiple libraries simultaneously.
NUKAT
The union catalogue of polish research library Collections.
KARO
Distributed Catalogue of Polish Libraries – a search tool collecting information from many polish bibliographical catalogues. It should be considered as a complementary tool to the Polish Union catalogue NUKAT.
The National Library central catalogues
The National Library collects information about foreign books and Polish and foreign periodicals held in Polish libraries. This information is made available through catalogs available on the National Library website.
WORLDCAT
The World's Largest Library Catalogue – a global catalogue of library collections.
RISM
An international central catalog containing descriptions of musical manuscripts, printed works, theoretical treatises, and librettos. These are sources held in libraries, archives, churches, private collections, and others. RISM determines what sources exist and where they are stored. Many researchers consider RISM the primary source of information on musical sources worldwide.