MLA

Koch, Frederick R. (Frederick Robinson). Music/Geneviève de Brabant. Box 329, folder 1834. 1875 Feb 2. https://collections.library.yale.edu/catalog/12218303.

APA, 6th edition

Koch, Frederick R. (Frederick Robinson). (["Box 329, folder 1834"])(1875 Feb 2)[Music/Geneviève de Brabant]. https://collections.library.yale.edu/catalog/12218303.