MLA

Robert Walpole, Father of Lord Walpole from an Original at Wolterton. [Graphic]. Pub. Feb. 1, 1801 [that is, 1802], by the Revd. W. Coxe, London, 0AD. https://collections.library.yale.edu/catalog/16193408.

APA, 6th edition

Robert Walpole, father of Lord Walpole from an original at Wolterton. [graphic]. (0 C.E.). [Book illustrations, Portrait prints, Stipple engravings England London 1802]. Pub. Feb. 1, 1801 [that is, 1802], by the Revd. W. Coxe, London. https://collections.library.yale.edu/catalog/16193408.