MLA

Josephson, Matthew, 1899-1978. Frankfurter, Felix. Box 4, folder 93. 1940-52, n.d.. https://collections.library.yale.edu/catalog/17091493.

APA, 6th edition

Josephson, Matthew, 1899-1978. (["Box 4, folder 93"])(1940-52, n.d.)[Frankfurter, Felix]. https://collections.library.yale.edu/catalog/17091493.