MLA

Wilder, Thornton, 1897-1975. Correspondence. Box 6, folder 126. 1947. https://collections.library.yale.edu/catalog/17418515.

APA, 6th edition

Wilder, Thornton, 1897-1975. (["Box 6, folder 126"])(1947)[Correspondence]. https://collections.library.yale.edu/catalog/17418515.