MLA

Leoncavallo, Ruggiero, 1858-1919. Vaucaire, Maurice. Box 10, folder 306. [1906]. https://collections.library.yale.edu/catalog/17353477.

APA, 6th edition

Leoncavallo, Ruggiero, 1858-1919. (["Box 10, folder 306"])([1906])[Vaucaire, Maurice]. https://collections.library.yale.edu/catalog/17353477.