MLA

Wharton, Edith, 1862-1937. The American Magazine. Box 31, folder 960. 1919-20. https://collections.library.yale.edu/catalog/17111166.

APA, 6th edition

Wharton, Edith, 1862-1937. (["Box 31, folder 960"])(1919-20)[The American Magazine]. https://collections.library.yale.edu/catalog/17111166.