MLA

Huntington, Ellsworth, 1876-1947. B. Box 1, folder 3. 1947, undated. https://collections.library.yale.edu/catalog/32507042.

APA, 6th edition

Huntington, Ellsworth, 1876-1947. (["Box 1, folder 3"])(1947, undated)[B]. https://collections.library.yale.edu/catalog/32507042.