MLA

Simpson, Randolph Linsly, 1927-1992. Unknown printer "Cook shanty, Jr. O.U.A.M. Regiment Camp:" Four chefs stand before shanty. Postcard. Box 25, folder 1036. circa 1900. https://collections.library.yale.edu/catalog/32312584.

APA, 6th edition

Simpson, Randolph Linsly, 1927-1992. (["Box 25, folder 1036"])(circa 1900)[Unknown printer "Cook shanty, Jr. O.U.A.M. Regiment Camp:" Four chefs stand before shanty. Postcard]. https://collections.library.yale.edu/catalog/32312584.