MLA

Stieglitz, Alfred, 1864-1946. Warhol, Andy. Box 218, folder 3877. 1980. https://collections.library.yale.edu/catalog/11021523.

APA, 6th edition

Stieglitz, Alfred, 1864-1946. (["Box 218, folder 3877"])(1980)[Warhol, Andy]. https://collections.library.yale.edu/catalog/11021523.