MLA

Simpson, Randolph Linsly, 1927-1992. W. B. Garrison, Washington, D. C. "In Line for Mess, Colored Section, Camp Humphreys, Va." Postcard. Box 25. circa 1917. https://collections.library.yale.edu/catalog/16172722.

APA, 6th edition

Simpson, Randolph Linsly, 1927-1992. (["Box 25"])(circa 1917)[W. B. Garrison, Washington, D. C. "In Line for Mess, Colored Section, Camp Humphreys, Va." Postcard]. https://collections.library.yale.edu/catalog/16172722.