MLA

Stieglitz, Alfred, 1864-1946. Letters. Box 63, folder 1432-1433. 1923 Sep. https://collections.library.yale.edu/catalog/2039837.

APA, 6th edition

Stieglitz, Alfred, 1864-1946. (["Box 63, folder 1432-1433"])(1923 Sep)[Letters]. https://collections.library.yale.edu/catalog/2039837.