MLA

Butts, Mary, 1890-1937. The Cornhill Magazine. Box 1, folder 16. 1934-36. https://collections.library.yale.edu/catalog/16893643.

APA, 6th edition

Butts, Mary, 1890-1937. (["Box 1, folder 16"])(1934-36)[The Cornhill Magazine]. https://collections.library.yale.edu/catalog/16893643.