MLA

Keller, Deane, 1901-1992. San Leonardo. Box 36, folder 227. 1945, undated. https://collections.library.yale.edu/catalog/10019244.

APA, 6th edition

Keller, Deane, 1901-1992. (["Box 36, folder 227"])(1945, undated)[San Leonardo]. https://collections.library.yale.edu/catalog/10019244.