MLA

Hartley, Marsden, 1877-1943. Letters. Box 8. 1900-1933. https://collections.library.yale.edu/catalog/16827253.

APA, 6th edition

Hartley, Marsden, 1877-1943. (["Box 8"])(1900-1933)[Letters]. https://collections.library.yale.edu/catalog/16827253.