MLA

Miłosz, Czesław, 1911-2004. Whitman, Walt. Box 141, folder 2245. 1978?, undated. https://collections.library.yale.edu/catalog/10079806.

APA, 6th edition

Miłosz, Czesław, 1911-2004. (["Box 141, folder 2245"])(1978?, undated)[Whitman, Walt]. https://collections.library.yale.edu/catalog/10079806.