MLA

Stieglitz, Alfred, 1864-1946. Caffin, Charles H.; Caffin, Caroline; Caffin, Freda. Box 9, folder 199. 1901-18, n.d.. https://collections.library.yale.edu/catalog/17414985.

APA, 6th edition

Stieglitz, Alfred, 1864-1946. (["Box 9, folder 199"])(1901-18, n.d.)[Caffin, Charles H.; Caffin, Caroline; Caffin, Freda]. https://collections.library.yale.edu/catalog/17414985.