MLA

Doctor Gruel [Graphic]. Pubd. according to act of Parlt., Oct. 3d, 1771, by MDarly, 39 Strand, 0AD. https://collections.library.yale.edu/catalog/10715774.

APA, 6th edition

Doctor Gruel [graphic]. (0 C.E.). [Caricatures and cartoons, Satires (Visual works) England 1771, Etchings England London 1771]. Pubd. according to act of Parlt., Oct. 3d, 1771, by MDarly, 39 Strand. https://collections.library.yale.edu/catalog/10715774.