MLA

Luhan, Mabel Dodge, 1879-1962. Wilder, Thornton. Box 65, folder 1779. n.d.. https://collections.library.yale.edu/catalog/16587317.

APA, 6th edition

Luhan, Mabel Dodge, 1879-1962. (["Box 65, folder 1779"])(n.d.)[Wilder, Thornton]. https://collections.library.yale.edu/catalog/16587317.