MLA

Butts, Mary, 1890-1937. Davenport, John. Box 1, folder 20. 1932 Dec 12. https://collections.library.yale.edu/catalog/16893647.

APA, 6th edition

Butts, Mary, 1890-1937. (["Box 1, folder 20"])(1932 Dec 12)[Davenport, John]. https://collections.library.yale.edu/catalog/16893647.