MLA

Cohen, Felix S., 1907-1953. Chief, Elizabeth. Box 50, folder 759. 1949-50. https://collections.library.yale.edu/catalog/9998336.

APA, 6th edition

Cohen, Felix S., 1907-1953. (["Box 50, folder 759"])(1949-50)[Chief, Elizabeth]. https://collections.library.yale.edu/catalog/9998336.