MLA

[Drawing of Two Classical Figures] [Art Original]. 0AD. https://collections.library.yale.edu/catalog/16873233.

APA, 6th edition

[Drawing of two classical figures] [art original]. (0 C.E.). [Female figure drawings, Male figure drawings, Graphite drawings British 18th century, Ink drawings British 18th century]. https://collections.library.yale.edu/catalog/16873233.