MLA

Ernest Augustus, King of Hanover, 1771-1851. Music book. Box 830. circa 1829-1839. https://collections.library.yale.edu/catalog/10000245.

APA, 6th edition

Ernest Augustus, King of Hanover, 1771-1851. (["Box 830"])(circa 1829-1839)[Music book]. https://collections.library.yale.edu/catalog/10000245.