MLA

Williams, William Carlos, 1883-1963. "Measure: A study of that which has occurred in the development of the poetical line in modern times"". Box 43, folder 1082-1084. undated. https://collections.library.yale.edu/catalog/17049583.

APA, 6th edition

Williams, William Carlos, 1883-1963. (["Box 43, folder 1082-1084"])(undated)["Measure: A study of that which has occurred in the development of the poetical line in modern times""]. https://collections.library.yale.edu/catalog/17049583.