MLA

Lewis, Sinclair, 1885-1951. "America Unabashed," review. Box 35, folder 272. undated. https://collections.library.yale.edu/catalog/17116517.

APA, 6th edition

Lewis, Sinclair, 1885-1951. (["Box 35, folder 272"])(undated)["America Unabashed," review]. https://collections.library.yale.edu/catalog/17116517.