MLA

Duse, Eleonora, 1858-1924. Letter to Gabriele d'Annunzio. Box 1 | Folder 1. 1896 February 14. https://collections.library.yale.edu/catalog/15809598.

APA, 6th edition

Duse, Eleonora, 1858-1924. (["Box 1 | Folder 1"])(1896 February 14)[Letter to Gabriele d'Annunzio]. https://collections.library.yale.edu/catalog/15809598.