MLA

Stead, William Force, 1884-1967. Lewis, Clive Staples, 1898-1963. Box 2. 1937 August. https://collections.library.yale.edu/catalog/16830017.

APA, 6th edition

Stead, William Force, 1884-1967. (["Box 2"])(1937 August)[Lewis, Clive Staples, 1898-1963]. https://collections.library.yale.edu/catalog/16830017.