MLA

Stieglitz, Alfred, 1864-1946. Kasebier, Gertrude. Box 26, folder 629. 1899-1914, n.d.. https://collections.library.yale.edu/catalog/17105636.

APA, 6th edition

Stieglitz, Alfred, 1864-1946. (["Box 26, folder 629"])(1899-1914, n.d.)[Kasebier, Gertrude]. https://collections.library.yale.edu/catalog/17105636.