MLA

Koch, Frederick R. (Frederick Robinson). Music/Troilus and Cressida, act III: score. Box 223, folder 1565. [1947]-54. https://collections.library.yale.edu/catalog/2067780.

APA, 6th edition

Koch, Frederick R. (Frederick Robinson). (["Box 223, folder 1565"])([1947]-54)[Music/Troilus and Cressida, act III: score]. https://collections.library.yale.edu/catalog/2067780.