Cite

[No. 75: Photograph of horses descending steep slope]

MLA

[No. 75: Photograph of Horses Descending Steep Slope]. 1915. https://collections.library.yale.edu/catalog/11680007.

APA, 6th edition

[No. 75: Photograph of horses descending steep slope]. (1915). [Photographs, Slides (glass)]. https://collections.library.yale.edu/catalog/11680007.