MLA

Map, Sanborn, and issuing body Publishing Co. Portland, Middlesex Co., Conn. 1889. https://collections.library.yale.edu/catalog/11593814.

APA, 6th edition

Map, S., & Publishing Co., issuing body. (1889). Portland, Middlesex Co., Conn. [Atlases--Connecticut--Portland--1889, Cadastral maps--Connecticut--Portland--1889, Fire insurance maps--Connecticut--Portland--1889]. https://collections.library.yale.edu/catalog/11593814.