MLA

Wilder, Thornton, 1897-1975. Miłosz, Czesław. Box 49, folder 1317. 1947 May 23. https://collections.library.yale.edu/catalog/10034604.

APA, 6th edition

Wilder, Thornton, 1897-1975. (["Box 49, folder 1317"])(1947 May 23)[Miłosz, Czesław]. https://collections.library.yale.edu/catalog/10034604.