MLA

Sergeant, Elizabeth Shepley, 1881-1965. Howard, Sidney. Box 3, folder 83-85. 1917-19. https://collections.library.yale.edu/catalog/10520876.

APA, 6th edition

Sergeant, Elizabeth Shepley, 1881-1965. (["Box 3, folder 83-85"])(1917-19)[Howard, Sidney]. https://collections.library.yale.edu/catalog/10520876.