MLA

Stieglitz, Alfred, 1864-1946. Letters. Box 87, folder 1741-1742. 1931 Oct-Nov. https://collections.library.yale.edu/catalog/2040491.

APA, 6th edition

Stieglitz, Alfred, 1864-1946. (["Box 87, folder 1741-1742"])(1931 Oct-Nov)[Letters]. https://collections.library.yale.edu/catalog/2040491.