MLA

Simpson, Randolph Linsly, 1927-1992. Alexander Gardner, Washington, DC Mounted verso: "Photographic Incidents of the War. No. 802. Part of Federal Line of Works showing Bombproof Tents occupied by U.S. Colored Troops in front of Petersburg, Va., Aug. 7, 1864." Stereograph, yellow card. Box 12, folder 551. circa 1864. https://collections.library.yale.edu/catalog/2005530.

APA, 6th edition

Simpson, Randolph Linsly, 1927-1992. (["Box 12, folder 551"])(circa 1864)[Alexander Gardner, Washington, DC Mounted verso: "Photographic Incidents of the War. No. 802. Part of Federal Line of Works showing Bombproof Tents occupied by U.S. Colored Troops in front of Petersburg, Va., Aug. 7, 1864." Stereograph, yellow card]. https://collections.library.yale.edu/catalog/2005530.