MLA

Simpson, Randolph Linsly, 1927-1992. [Alexander] Gardner's Gallery, Washington, D.C. Mounted verso, "Photographic Incidents of the War. No. 382. Gen'ls Barry, Slocum, Newton, Franklin, and Friends, May 14, 1862." Stereograph, yellow card. Box 12, folder 550. circa 1862. https://collections.library.yale.edu/catalog/2111707.

APA, 6th edition

Simpson, Randolph Linsly, 1927-1992. (["Box 12, folder 550"])(circa 1862)[[Alexander] Gardner's Gallery, Washington, D.C. Mounted verso, "Photographic Incidents of the War. No. 382. Gen'ls Barry, Slocum, Newton, Franklin, and Friends, May 14, 1862." Stereograph, yellow card]. https://collections.library.yale.edu/catalog/2111707.