MLA

Drinkwater, John, 1882-1937. Arlen, Michael, 1895-. ALS, Paris. Box 1, folder 8. n.y.. https://collections.library.yale.edu/catalog/17280579.

APA, 6th edition

Drinkwater, John, 1882-1937. (["Box 1, folder 8"])(n.y.)[Arlen, Michael, 1895-. ALS, Paris]. https://collections.library.yale.edu/catalog/17280579.