MLA

Stieglitz, Alfred, 1864-1946. Letters. Box 63, folder 1444. 1927 Dec. https://collections.library.yale.edu/catalog/2039849.

APA, 6th edition

Stieglitz, Alfred, 1864-1946. (["Box 63, folder 1444"])(1927 Dec)[Letters]. https://collections.library.yale.edu/catalog/2039849.