MLA

Butts, Mary, 1890-1937. Butts, Frederick John. Box 1, folder 5. n.d.. https://collections.library.yale.edu/catalog/16893633.

APA, 6th edition

Butts, Mary, 1890-1937. (["Box 1, folder 5"])(n.d.)[Butts, Frederick John]. https://collections.library.yale.edu/catalog/16893633.