MLA

Van Sinderen, Alfred White, 1924-1998. Babbage, Benjamin Herschel. Box 1, folder 2. undated. https://collections.library.yale.edu/catalog/30997386.

APA, 6th edition

Van Sinderen, Alfred White, 1924-1998. (["Box 1, folder 2"])(undated)[Babbage, Benjamin Herschel]. https://collections.library.yale.edu/catalog/30997386.