MLA

Broch, Hermann, 1886-1951. Sonne, Abraham. Box 12, folder 365. 1944-50. https://collections.library.yale.edu/catalog/17268001.

APA, 6th edition

Broch, Hermann, 1886-1951. (["Box 12, folder 365"])(1944-50)[Sonne, Abraham]. https://collections.library.yale.edu/catalog/17268001.