MLA

Lewis, Sinclair, 1885-1951. Drafts. Box 6, folder 43-45. 1927, undated. https://collections.library.yale.edu/catalog/32257693.

APA, 6th edition

Lewis, Sinclair, 1885-1951. (["Box 6, folder 43-45"])(1927, undated)[Drafts]. https://collections.library.yale.edu/catalog/32257693.