Official definition
This industry comprises establishments primarily engaged in providing library or archive services. These establishments maintain collections of documents (such as books, journals, newspapers and music) and facilitate the use of such documents (regardless of its physical form and characteristics) as are required to meet the informational, research, educational or recreational needs of their users. They may also acquire, research, store, and make accessible to the public, original historical documents, photographs, maps, audio material, audio-visual material and other archival materials of historical interest. Cinematheques, videotheques and other film and video archives, whose primary purpose is the preservation of archival audio-visual material, are included. All or portions of these collections may be accessible electronically.