MLA

Miłosz, Czesław, 1911-2004. Faulkner, William. Box 137, folder 2176. undated. https://collections.library.yale.edu/catalog/10090500.

APA, 6th edition

Miłosz, Czesław, 1911-2004. (["Box 137, folder 2176"])(undated)[Faulkner, William]. https://collections.library.yale.edu/catalog/10090500.