MLA

Stieglitz, Alfred, 1864-1946. Rosenfeld, Paul. Box 212, folder 3722. 1921-45. https://collections.library.yale.edu/catalog/32416614.

APA, 6th edition

Stieglitz, Alfred, 1864-1946. (["Box 212, folder 3722"])(1921-45)[Rosenfeld, Paul]. https://collections.library.yale.edu/catalog/32416614.