MLA

Section, Great Britain. War Office. General Staff. Geographical. Straits of Gibraltar [Cartographic Material]. War Office, 1919. https://collections.library.yale.edu/catalog/15487372.

APA, 6th edition

Section, G. B. W. O. G. S. G. (1919). Straits of Gibraltar [cartographic material]. [Topographic maps]. War Office, https://collections.library.yale.edu/catalog/15487372.