MLA

Hartley, Marsden, 1877-1943. "Hart Crane". Box 1. undated. https://collections.library.yale.edu/catalog/16721053.

APA, 6th edition

Hartley, Marsden, 1877-1943. (["Box 1"])(undated)["Hart Crane"]. https://collections.library.yale.edu/catalog/16721053.