MLA

Stieglitz, Alfred, 1864-1946. Letters. Box 69, folder 1507-1518. 1933 Jan-Jun. https://collections.library.yale.edu/catalog/2041198.

APA, 6th edition

Stieglitz, Alfred, 1864-1946. (["Box 69, folder 1507-1518"])(1933 Jan-Jun)[Letters]. https://collections.library.yale.edu/catalog/2041198.