The Virtual International Authority File (VIAF) is an international authority file. It is a joint project of several national libraries
IdRef is the authority database (author, title) of the union catalogue for France's higher education libraries (SUDOC)
ISNI is an international certified number (ISO 27729) that uniquely identifies persons and organisations.
MusicBrainz is an open music encyclopedia that collects music metadata and makes it available to the public.