MLA

Matthiessen, F. O. (Francis Otto), 1902-1950. Einstein, Albert. Box 2. 1948. https://collections.library.yale.edu/catalog/32239639.

APA, 6th edition

Matthiessen, F. O. (Francis Otto), 1902-1950. (["Box 2"])(1948)[Einstein, Albert]. https://collections.library.yale.edu/catalog/32239639.