MLA

Walpole, Horace, 1717-1797, collector. Drawings and designs by Richd. Bentley, only son of Dr. Bentley, Master of Trinity-College, Cambridge [art original].. [approximately 1760]. https://collections.library.yale.edu/catalog/15952290.

APA, 6th edition

Walpole, Horace, 1717-1797, collector. ([approximately 1760])[Drawings and designs by Richd. Bentley, only son of Dr. Bentley, Master of Trinity-College, Cambridge [art original].]. https://collections.library.yale.edu/catalog/15952290.