MLA

Williams, William Carlos, 1883-1963. "Vs.". Box 45, folder 1136. undated. https://collections.library.yale.edu/catalog/17049594.

APA, 6th edition

Williams, William Carlos, 1883-1963. (["Box 45, folder 1136"])(undated)["Vs."]. https://collections.library.yale.edu/catalog/17049594.