MLA

Ford, Julia Ellsworth, 1859-1950. Beaux, Cecilia. Box 1, folder 7. 1914 June 8. https://collections.library.yale.edu/catalog/17167804.

APA, 6th edition

Ford, Julia Ellsworth, 1859-1950. (["Box 1, folder 7"])(1914 June 8)[Beaux, Cecilia]. https://collections.library.yale.edu/catalog/17167804.