MLA

Stieglitz, Alfred, 1864-1946. Letters. Box 85, folder 1723-1724. 1930 Apr-May. https://collections.library.yale.edu/catalog/2039984.

APA, 6th edition

Stieglitz, Alfred, 1864-1946. (["Box 85, folder 1723-1724"])(1930 Apr-May)[Letters]. https://collections.library.yale.edu/catalog/2039984.