MLA

Matthiessen, F. O. (Francis Otto), 1902-1950. McWilliams, Carey. Box 3. 1930-1949. https://collections.library.yale.edu/catalog/32239746.

APA, 6th edition

Matthiessen, F. O. (Francis Otto), 1902-1950. (["Box 3"])(1930-1949)[McWilliams, Carey]. https://collections.library.yale.edu/catalog/32239746.