MLA

Great Britain. War Office. General Staff. Geographical Section, United States. Army Map Service. S. Tiago / Drawn at War Office, 1940, from a Portuguese Map of 1932. Army Map Service, 1943. https://collections.library.yale.edu/catalog/15238422.

APA, 6th edition

Great Britain. War Office. General Staff. Geographical Section, U. S. A. M. S. (1943). S. Tiago / drawn at War Office, 1940, from a Portuguese map of 1932 [Maps]. Army Map Service, https://collections.library.yale.edu/catalog/15238422.