MLA

Williams, William Carlos, 1883-1963. Orlovitz, Gil. Box 17, folder 550. 1950. https://collections.library.yale.edu/catalog/17049524.

APA, 6th edition

Williams, William Carlos, 1883-1963. (["Box 17, folder 550"])(1950)[Orlovitz, Gil]. https://collections.library.yale.edu/catalog/17049524.