MLA

Miłosz, Czesław, 1911-2004. Lindsay, Vachel. Box 138, folder 2193. undated. https://collections.library.yale.edu/catalog/10090659.

APA, 6th edition

Miłosz, Czesław, 1911-2004. (["Box 138, folder 2193"])(undated)[Lindsay, Vachel]. https://collections.library.yale.edu/catalog/10090659.