MLA

Schreyvogel, Charles, 1861-1912, artist. The attackers. [1900?]. https://collections.library.yale.edu/catalog/2016614.

APA, 6th edition

Schreyvogel, Charles, 1861-1912, artist. ([1900?])[The attackers]. https://collections.library.yale.edu/catalog/2016614.