MLA

James, Rebecca Salsbury, 1891-1968. Duncan, Charles. Box 1, folder 3. [1928?]. https://collections.library.yale.edu/catalog/17059990.

APA, 6th edition

James, Rebecca Salsbury, 1891-1968. (["Box 1, folder 3"])([1928?])[Duncan, Charles]. https://collections.library.yale.edu/catalog/17059990.