MLA

Butts, Mary, 1890-1937. Mayne, Ethel Colburn. Box 1, folder 32. 1922-35. https://collections.library.yale.edu/catalog/16893659.

APA, 6th edition

Butts, Mary, 1890-1937. (["Box 1, folder 32"])(1922-35)[Mayne, Ethel Colburn]. https://collections.library.yale.edu/catalog/16893659.