Cite

Look at the obstacle race over a barrier 2 horses down with a soldier on one, etc.

MLA

Hecox, Frank C. Look at the Obstacle Race over a Barrier 2 Horses down with a Soldier on One, Etc. 1915. https://collections.library.yale.edu/catalog/2015349.

APA, 6th edition

Hecox, F. C. (1915). Look at the obstacle race over a barrier 2 horses down with a soldier on one, etc. [Photographic postcards, Photographic prints, Photographs]. https://collections.library.yale.edu/catalog/2015349.