MLA

Stieglitz, Alfred, 1864-1946. Ringel, Frederick Julius. Box 41, folder 984. 1932-43. https://collections.library.yale.edu/catalog/10933029.

APA, 6th edition

Stieglitz, Alfred, 1864-1946. (["Box 41, folder 984"])(1932-43)[Ringel, Frederick Julius]. https://collections.library.yale.edu/catalog/10933029.