MLA

Ford, Julia Ellsworth, 1859-1950. Hampden, Walter. Box 1, folder 34. 1933 April 1. https://collections.library.yale.edu/catalog/17167831.

APA, 6th edition

Ford, Julia Ellsworth, 1859-1950. (["Box 1, folder 34"])(1933 April 1)[Hampden, Walter]. https://collections.library.yale.edu/catalog/17167831.