MLA

Stieglitz, Alfred, 1864-1946. Letter. Box 83, folder 1691. 1918 Sep 17. https://collections.library.yale.edu/catalog/2039552.

APA, 6th edition

Stieglitz, Alfred, 1864-1946. (["Box 83, folder 1691"])(1918 Sep 17)[Letter]. https://collections.library.yale.edu/catalog/2039552.