MLA

Stieglitz, Alfred, 1864-1946. Rainer, Luise. Box 40, folder 958. 1937-40. https://collections.library.yale.edu/catalog/17105648.

APA, 6th edition

Stieglitz, Alfred, 1864-1946. (["Box 40, folder 958"])(1937-40)[Rainer, Luise]. https://collections.library.yale.edu/catalog/17105648.