MLA

Stieglitz, Alfred, 1864-1946. Letters. Box 93, folder 1838. 1943 Jan. https://collections.library.yale.edu/catalog/2044035.

APA, 6th edition

Stieglitz, Alfred, 1864-1946. (["Box 93, folder 1838"])(1943 Jan)[Letters]. https://collections.library.yale.edu/catalog/2044035.