MLA

Ernest Augustus, King of Hanover, 1771-1851. Trio for the Harpsichord or piano Forte with an Accompaniment for a Flauto & Violoncello Obligato... Parts (kbd, fl, vc). Manuscript. Box 118, folder 604. undated. https://collections.library.yale.edu/catalog/15789743.

APA, 6th edition

Ernest Augustus, King of Hanover, 1771-1851. (["Box 118, folder 604"])(undated)[Trio for the Harpsichord or piano Forte with an Accompaniment for a Flauto & Violoncello Obligato... Parts (kbd, fl, vc). Manuscript]. https://collections.library.yale.edu/catalog/15789743.