The "Beluga" catalog will enable you to search for books and other media of research libraries in the city. You will also find several million electronic documents that can be accessed by users free of charge under German national licensing.
The Union Catalog (GVK) is the freely accessible section of the Common Library Network database. The GVK lists more than 41.5 million titles, with more than 105 million separate catalog entries in some 500 libraries.
The ZDB, the German Union Catalogue of Serials, is the world’s largest database for titles and local holdings information in German libraries of serial publications, journals, and newspapers in printed and electronic editions.