MLA

Huntington, Ellsworth, 1876-1947. C. Box 1, folder 4. 1947, undated. https://collections.library.yale.edu/catalog/32507045.

APA, 6th edition

Huntington, Ellsworth, 1876-1947. (["Box 1, folder 4"])(1947, undated)[C]. https://collections.library.yale.edu/catalog/32507045.