Cite

A key for Mr. Copley's plate of the Death of the late Earl of Chatham [graphic].

MLA

A Key for Mr. Copley's Plate of the Death of the Late Earl of Chatham [Graphic]. Published by John Singleton Copley, R.A., Decr. 26, 1791, and sold at Parr's Print Warehouse, No. 52 Pall Mall, 0AD. https://collections.library.yale.edu/catalog/33111840.

APA, 6th edition

A key for Mr. Copley's plate of the Death of the late Earl of Chatham [graphic]. (0 C.E.). [Group portraits, Portrait prints, Keys (Legends), Engravings England London 1791]. Published by John Singleton Copley, R.A., Decr. 26, 1791, and sold at Parr's Print Warehouse, No. 52 Pall Mall. https://collections.library.yale.edu/catalog/33111840.