MLA

Service, United States. Army Map. Valletta City Plan [Cartographic Material] / Prepared under the Direction of the Chief of Engineers, U.S. Army 1943. Army Map Service, U.S. Army, 1943. https://collections.library.yale.edu/catalog/15502088.

APA, 6th edition

Service, U. S. A. M. (1943). Valletta city plan [cartographic material] / prepared under the direction of the Chief of Engineers, U.S. Army 1943. [Maps]. Army Map Service, U.S. Army, https://collections.library.yale.edu/catalog/15502088.