MLA

Helmets. [Graphic]. Pl. 62. Pub. 28 May 1789 by S. Hooper, 0AD. https://collections.library.yale.edu/catalog/16193024.

APA, 6th edition

Helmets. [graphic]. Pl. 62. (0 C.E.). [Book illustrations, Etchings England London 1789, Engravings England London 1789]. Pub. 28 May 1789 by S. Hooper. https://collections.library.yale.edu/catalog/16193024.