MLA

Stieglitz, Alfred, 1864-1946. Letters. Box 91, folder 1796-1799. 1939 Jan-Apr. https://collections.library.yale.edu/catalog/2042809.

APA, 6th edition

Stieglitz, Alfred, 1864-1946. (["Box 91, folder 1796-1799"])(1939 Jan-Apr)[Letters]. https://collections.library.yale.edu/catalog/2042809.