MLA

James, Rebecca Salsbury, 1891-1968. Luhan, Mabel Dodge. Box 1, folder 25. [1929?]. https://collections.library.yale.edu/catalog/2003727.

APA, 6th edition

James, Rebecca Salsbury, 1891-1968. (["Box 1, folder 25"])([1929?])[Luhan, Mabel Dodge]. https://collections.library.yale.edu/catalog/2003727.