MLA

Stieglitz, Alfred, 1864-1946. Envelopes. Box 95, folder 1866. n.d.. https://collections.library.yale.edu/catalog/2052805.

APA, 6th edition

Stieglitz, Alfred, 1864-1946. (["Box 95, folder 1866"])(n.d.)[Envelopes]. https://collections.library.yale.edu/catalog/2052805.