Classification.
Class Z: Bibliography and library science.

APA Citation

Library of Congress. Classification Division., Skinner, E. Jane., Starr, H. Knowlton., Martel, C. (1927). Classification: Class Z: Bibliography and library science. 3d ed. January, 1926. Washington: U.S. Govt. print. off..

MLA Citation

Library of Congress. Classification Division, Eliza Jane Skinner, Helen Knowlton Starr, and Charles Martel. Classification: Class Z: Bibliography And Library Science. 3d ed. January, 1926. Washington: U.S. Govt. print. off., 1927.