MLA

Broch, Hermann, 1886-1951. Norden, Ruth. Box 19, folder 610. 1940 Nov 19. https://collections.library.yale.edu/catalog/17268012.

APA, 6th edition

Broch, Hermann, 1886-1951. (["Box 19, folder 610"])(1940 Nov 19)[Norden, Ruth]. https://collections.library.yale.edu/catalog/17268012.