MLA

Fairholt, F. W. (Frederick William), 1814-1866, artist. Ponte alle Grazie, Florence [art original]. [ca. 1856?]. https://collections.library.yale.edu/catalog/15960394.

APA, 6th edition

Fairholt, F. W. (Frederick William), 1814-1866, artist. ([ca. 1856?])[Ponte alle Grazie, Florence [art original]]. https://collections.library.yale.edu/catalog/15960394.