MLA

Harding, G. P. (George Perfect), 1780-1853, artist. Richard Sackville Baron Buckhurst and Earl Dorset [art original]. [1799]. https://collections.library.yale.edu/catalog/11138653.

APA, 6th edition

Harding, G. P. (George Perfect), 1780-1853, artist. ([1799])[Richard Sackville Baron Buckhurst and Earl Dorset [art original]]. https://collections.library.yale.edu/catalog/11138653.