MLA

Sergeant, Elizabeth Shepley, 1881-1965. Luhan, Mabel Dodge. Box 5, folder 118. 1923-45, n.d.. https://collections.library.yale.edu/catalog/17054226.

APA, 6th edition

Sergeant, Elizabeth Shepley, 1881-1965. (["Box 5, folder 118"])(1923-45, n.d.)[Luhan, Mabel Dodge]. https://collections.library.yale.edu/catalog/17054226.