MLA

Stieglitz, Alfred, 1864-1946. Letters. Box 229, folder 4052-4066. 1977-83. https://collections.library.yale.edu/catalog/10577007.

APA, 6th edition

Stieglitz, Alfred, 1864-1946. (["Box 229, folder 4052-4066"])(1977-83)[Letters]. https://collections.library.yale.edu/catalog/10577007.