MLA

United States. Army. Signal Corps, Watkins, and cartographer J. H. Map of the Operations against Manila, Aug. 13, 1898 / J.H. Watkins. Norris Peters Co.?, 1898. https://collections.library.yale.edu/catalog/15239168.

APA, 6th edition

United States. Army. Signal Corps, W., & J. H., cartographer. (1898). Map of the operations against Manila, Aug. 13, 1898 / J.H. Watkins. [Maps]. Norris Peters Co.? https://collections.library.yale.edu/catalog/15239168.