MLA

Stieglitz, Alfred, 1864-1946. Ross, Cary. Box 212, folder 3723. 1940, 1951, n.d.. https://collections.library.yale.edu/catalog/32416636.

APA, 6th edition

Stieglitz, Alfred, 1864-1946. (["Box 212, folder 3723"])(1940, 1951, n.d.)[Ross, Cary]. https://collections.library.yale.edu/catalog/32416636.