Cite

Sitting Bull. [head and shoulders]

MLA

Gilbert, Z. (Zalmon), artist. Sitting Bull. [head and shoulders]. ca. 1880. https://collections.library.yale.edu/catalog/2009504.

APA, 6th edition

Gilbert, Z. (Zalmon), artist. (ca. 1880)[Sitting Bull. [head and shoulders]]. https://collections.library.yale.edu/catalog/2009504.