MLA

Walpole, Thomas, 1755-1840, artist. La Duchesse de Grammont, La Marechale de Luxembourg, L'abbé Biliardi, Madame de Luxembourg [art original]. [1782]. https://collections.library.yale.edu/catalog/33207415.

APA, 6th edition

Walpole, Thomas, 1755-1840, artist. ([1782])[La Duchesse de Grammont, La Marechale de Luxembourg, L'abbé Biliardi, Madame de Luxembourg [art original]]. https://collections.library.yale.edu/catalog/33207415.