MLA

Wharton, Edith, 1862-1937. Bosanquet, Theodora. Box 23, folder 723. 1910-15. https://collections.library.yale.edu/catalog/16781486.

APA, 6th edition

Wharton, Edith, 1862-1937. (["Box 23, folder 723"])(1910-15)[Bosanquet, Theodora]. https://collections.library.yale.edu/catalog/16781486.