MLA

Stieglitz, Alfred, 1864-1946. Letters. Box 223, folder 3982-3994. 1934-68. https://collections.library.yale.edu/catalog/10575579.

APA, 6th edition

Stieglitz, Alfred, 1864-1946. (["Box 223, folder 3982-3994"])(1934-68)[Letters]. https://collections.library.yale.edu/catalog/10575579.