APA (7th ed.) Citation

Library of Congress. (1975). The Library of Congress main reading room reference collection subject catalog. Library of Congress.

Chicago Style (17th ed.) Citation

Library of Congress. The Library of Congress Main Reading Room Reference Collection Subject Catalog. Washington: Library of Congress, 1975.

MLA (9th ed.) Citation

Library of Congress. The Library of Congress Main Reading Room Reference Collection Subject Catalog. Library of Congress, 1975.

Warning: These citations may not always be 100% accurate.