MLA

Wilder, Thornton, 1897-1975. Capote, Truman. Box 28, folder 672. 1959, n.d.. https://collections.library.yale.edu/catalog/17056642.

APA, 6th edition

Wilder, Thornton, 1897-1975. (["Box 28, folder 672"])(1959, n.d.)[Capote, Truman]. https://collections.library.yale.edu/catalog/17056642.