MLA

Stein, Gertrude, 1874-1946. Prints of photographs of artwork owned by, or featuring GS, and prints of artwork used in exhibition at the Yale University Art Gallery. Box 19, folder 323-325. n.d.. https://collections.library.yale.edu/catalog/2020674.

APA, 6th edition

Stein, Gertrude, 1874-1946. (["Box 19, folder 323-325"])(n.d.)[Prints of photographs of artwork owned by, or featuring GS, and prints of artwork used in exhibition at the Yale University Art Gallery]. https://collections.library.yale.edu/catalog/2020674.