MLA

Wilson, Edmund, 1895-1972. De Santillana, Dorothy. Box 21, folder 510. 1950, n.d.. https://collections.library.yale.edu/catalog/17083222.

APA, 6th edition

Wilson, Edmund, 1895-1972. (["Box 21, folder 510"])(1950, n.d.)[De Santillana, Dorothy]. https://collections.library.yale.edu/catalog/17083222.