Library of Congress & Subjet Cataloging Division. (1998). Subject Headings (21th. ed.). The National Bibliographic Service.

Library of Congress and Subjet Cataloging Division. Subject Headings. 21th. ed. Washington: The National Bibliographic Service, 1998.

Library of Congress and Subjet Cataloging Division. Subject Headings. 21th. ed. The National Bibliographic Service, 1998.