WorldCat is the world's largest network of library contents: more than 76 million of bibliographic records and more than 1.1 billion holdings' records. The number of bibliographic records are rising at a rate of 3.2 million records per year.
Materials in WorldCat have a wide variety of formats: books, serials, audio materials, scores, and maps etc. The languages of them are over 400.

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OCLC (Online Computer Library Center, Inc.) is a global library cooperative, joined by more than 50 thousand libraries from 84 countries and regions. Its headquarters is located in Dublin, Ohio State in the United States.

Major organizations joining OCLC: Library of Congress, British Library, university libraries like Harvard, Stanford and Oxford, and other institutions like NASA, Smithsonian Museum, the Metropolitan Museum of Art, and the World Bank, etc.