MLA

Section, Great Britain. General Staff. Geographical. Macao. [GSGS, War Office], 1918. https://collections.library.yale.edu/catalog/15510655.

APA, 6th edition

Section, G. B. G. S. G. (1918). Macao. [Maps]. [GSGS, War Office], https://collections.library.yale.edu/catalog/15510655.