MLA

Stieglitz, Alfred, 1864-1946. Duncan, Charles. Box 15, folder 356. 1916-32, n.d.. https://collections.library.yale.edu/catalog/17414987.

APA, 6th edition

Stieglitz, Alfred, 1864-1946. (["Box 15, folder 356"])(1916-32, n.d.)[Duncan, Charles]. https://collections.library.yale.edu/catalog/17414987.