MLA

Stieglitz, Alfred, 1864-1946. "Eduard J. Steichen". Box 130, folder 2511. ca. 1915. https://collections.library.yale.edu/catalog/2002550.

APA, 6th edition

Stieglitz, Alfred, 1864-1946. (["Box 130, folder 2511"])(ca. 1915)["Eduard J. Steichen"]. https://collections.library.yale.edu/catalog/2002550.