MLA

Stieglitz, Alfred, 1864-1946. Marsden Hartley. Box 124, folder 2475-2476. n.d.. https://collections.library.yale.edu/catalog/2017530.

APA, 6th edition

Stieglitz, Alfred, 1864-1946. (["Box 124, folder 2475-2476"])(n.d.)[Marsden Hartley]. https://collections.library.yale.edu/catalog/2017530.