MLA

Serge, Victor, 1890-1947. The American Magazine. Box 1, folder 3. 1941 Nov 24. https://collections.library.yale.edu/catalog/16495419.

APA, 6th edition

Serge, Victor, 1890-1947. (["Box 1, folder 3"])(1941 Nov 24)[The American Magazine]. https://collections.library.yale.edu/catalog/16495419.