- KVK
Karlsruhe Virtual Catalog
- worldcat
The world's largest library catalog. More than one billion titles in more than 10,000 libraries.
- libweb
Libweb currently lists over 8000 pages from libraries in 146 countries
- World Guide to Libraries
The World Guide to Libraries contains addresses and holdings information for more than 42,000 libraries in over 200 countries. It covers national libraries, research libraries, university libraries and faculty libraries. The search language is English.
- Zeitschriftendatenbank (ZDB)
The ZDB (journal database) directs readers to journals, newspapers and databases in German and Austrian libraries. The database is maintained jointly by 4,400 libraries.