MLA

Ford, Julia Ellsworth, 1859-1950. Yeats, Elizabeth Corbet. Box 3, folder 85. 1906-1939. https://collections.library.yale.edu/catalog/17167843.

APA, 6th edition

Ford, Julia Ellsworth, 1859-1950. (["Box 3, folder 85"])(1906-1939)[Yeats, Elizabeth Corbet]. https://collections.library.yale.edu/catalog/17167843.