MLA

Map, Sanborn, and issuing body Publishing Co. Essex, Middlesex Co., Conn. 1889. https://collections.library.yale.edu/catalog/11116903.

APA, 6th edition

Map, S., & Publishing Co., issuing body. (1889). Essex, Middlesex Co., Conn. [Atlases, Cadastral maps, Connecticut, Essex (Town), Fire insurance maps, local]. https://collections.library.yale.edu/catalog/11116903.