[Stepmother]
MLA
Lewis, Sinclair, 1885-1951. [Stepmother]. Box 54, folder 779. undated. https://collections.library.yale.edu/catalog/10516622.
APA, 6th edition
Lewis, Sinclair, 1885-1951. (["Box 54, folder 779"])(undated)[[Stepmother]]. https://collections.library.yale.edu/catalog/10516622.