MLA

Josephson, Matthew, 1899-1978. Powell, Thomas Reed. Box 9, folder 230. 1917-1979. https://collections.library.yale.edu/catalog/17091496.

APA, 6th edition

Josephson, Matthew, 1899-1978. (["Box 9, folder 230"])(1917-1979)[Powell, Thomas Reed]. https://collections.library.yale.edu/catalog/17091496.