MLA

Eaton, Edric L. Big Doctor. Eaton, 0AD. https://collections.library.yale.edu/catalog/2011418.

APA, 6th edition

Eaton, E. L. (0 C.E.). Big Doctor [Card photographs, Cartes-de-visite, Photographic prints, Photographs, Studio portraits]. Eaton. https://collections.library.yale.edu/catalog/2011418.