MLA

MacLeish, Archibald, 1892-1982. Choate, Elizabeth. Box 18, folder 339-42. 1920-27, n.d.. https://collections.library.yale.edu/catalog/17166960.

APA, 6th edition

MacLeish, Archibald, 1892-1982. (["Box 18, folder 339-42"])(1920-27, n.d.)[Choate, Elizabeth]. https://collections.library.yale.edu/catalog/17166960.