MLA

Stieglitz, Alfred, 1864-1946. Letters. Box 89, folder 1771. 1935 Feb-Mar. https://collections.library.yale.edu/catalog/2041994.

APA, 6th edition

Stieglitz, Alfred, 1864-1946. (["Box 89, folder 1771"])(1935 Feb-Mar)[Letters]. https://collections.library.yale.edu/catalog/2041994.