Cite

[Unknown gentleman in blue coat] [art original].

MLA

[Unknown Gentleman in Blue Coat] [Art Original]. 0AD. https://collections.library.yale.edu/catalog/15815163.

APA, 6th edition

[Unknown gentleman in blue coat] [art original]. (0 C.E.). [Portraits British 18th century, Watercolors British 18th century, Paintings British 18th century]. https://collections.library.yale.edu/catalog/15815163.