MLA

Leoncavallo, Ruggiero, 1858-1919. Unidentified. Box 10, folder 310. [ca. 1904]. https://collections.library.yale.edu/catalog/16666546.

APA, 6th edition

Leoncavallo, Ruggiero, 1858-1919. (["Box 10, folder 310"])([ca. 1904])[Unidentified]. https://collections.library.yale.edu/catalog/16666546.