MLA

Stieglitz, Alfred, 1864-1946. Goetz, Fritz. Box 21, folder 487. 1921-27, n.d.. https://collections.library.yale.edu/catalog/32188747.

APA, 6th edition

Stieglitz, Alfred, 1864-1946. (["Box 21, folder 487"])(1921-27, n.d.)[Goetz, Fritz]. https://collections.library.yale.edu/catalog/32188747.