Cite

[Maria, Duchess of Gloucester] [William Henry, Duke of Gloucester]. [art original]

MLA

Miers, John, 1789-1879, artist. [Maria, Duchess of Gloucester] [William Henry, Duke of Gloucester]. [art original]. [ca. 1790]. https://collections.library.yale.edu/catalog/15815218.

APA, 6th edition

Miers, John, 1789-1879, artist. ([ca. 1790])[[Maria, Duchess of Gloucester] [William Henry, Duke of Gloucester]. [art original]]. https://collections.library.yale.edu/catalog/15815218.