MLA

[Map Showing Fortifications around the Mouth of the San Juan River, Cuba during the War of 1898.]. publisher not identified, 0AD. https://collections.library.yale.edu/catalog/15832253.

APA, 6th edition

[Map showing fortifications around the mouth of the San Juan River, Cuba during the War of 1898.]. (0 C.E.). [Maps]. publisher not identified, https://collections.library.yale.edu/catalog/15832253.