MLA

Stieglitz, Alfred, 1864-1946. Letters. Box 84, folder 1700. 1926 Feb-Mar. https://collections.library.yale.edu/catalog/2039723.

APA, 6th edition

Stieglitz, Alfred, 1864-1946. (["Box 84, folder 1700"])(1926 Feb-Mar)[Letters]. https://collections.library.yale.edu/catalog/2039723.