The National Union Catalog (NUC) is a printed catalog of books catalogued by the Library of Congress and other American and Canadian libraries, issued beginning in the 1950s. The National Union Catalog is divided into two series: the Pre-1956 Imprints is a 754-volume set containing all older records in a consolidated alphabetical format, while post-1955 volumes continue to be published serially. Since 1983, the NUC has been issued on microfiche.[1] It is not related to the National Union Catalog of Manuscript Collections (NUCMC).[2]