Cite

[Maria, Duchess of Gloucester] [art original].

MLA

Shelley, Samuel, approximately 1750-1808, artist. [Maria, Duchess of Gloucester] [art original].. [ca. 1775]. https://collections.library.yale.edu/catalog/15815224.

APA, 6th edition

Shelley, Samuel, approximately 1750-1808, artist. ([ca. 1775])[[Maria, Duchess of Gloucester] [art original].]. https://collections.library.yale.edu/catalog/15815224.