MLA

Wilson, Edmund, 1895-1972. EW. Box 198, folder 4821. n.d.. https://collections.library.yale.edu/catalog/2008062.

APA, 6th edition

Wilson, Edmund, 1895-1972. (["Box 198, folder 4821"])(n.d.)[EW]. https://collections.library.yale.edu/catalog/2008062.