MLA

Schutz, Alfred, 1899-1959. Correspondence. Box 30, folder 765. 1939 Dec 15. https://collections.library.yale.edu/catalog/17301765.

APA, 6th edition

Schutz, Alfred, 1899-1959. (["Box 30, folder 765"])(1939 Dec 15)[Correspondence]. https://collections.library.yale.edu/catalog/17301765.