MLA

Broch, Hermann, 1886-1951. Einstein, Albert. Box 17, folder 480. 1944. https://collections.library.yale.edu/catalog/17268008.

APA, 6th edition

Broch, Hermann, 1886-1951. (["Box 17, folder 480"])(1944)[Einstein, Albert]. https://collections.library.yale.edu/catalog/17268008.