MLA

Sanborn Map Company, issuing body. Insurance Maps of Norwalk, Fairfield County, Connecticut. 1912. https://collections.library.yale.edu/catalog/11580358.

APA, 6th edition

Sanborn Map Company, issuing body. (1912). Insurance maps of Norwalk, Fairfield County, Connecticut. [Atlases--Connecticut--Norwalk--1912, Cadastral maps--Connecticut--Norwalk--1912, Fire insurance maps--Connecticut--Norwalk--1912]. https://collections.library.yale.edu/catalog/11580358.