MLA

Butts, Mary, 1890-1937. Desbordes, Jean. Box 1, folder 21. 1928 Aug 18, n.d.. https://collections.library.yale.edu/catalog/16893648.

APA, 6th edition

Butts, Mary, 1890-1937. (["Box 1, folder 21"])(1928 Aug 18, n.d.)[Desbordes, Jean]. https://collections.library.yale.edu/catalog/16893648.