Cite

[No. 69: Photograph of horses on a steep slope]

MLA

[No. 69: Photograph of Horses on a Steep Slope]. 1915. https://collections.library.yale.edu/catalog/11679668.

APA, 6th edition

[No. 69: Photograph of horses on a steep slope]. (1915). [Photographs, Portraits, Slides (glass)]. https://collections.library.yale.edu/catalog/11679668.