MLA

Sanborn Map Company, issuing body. Insurance Maps of Norwalk, Connecticut. 1922. https://collections.library.yale.edu/catalog/11580359.

APA, 6th edition

Sanborn Map Company, issuing body. (1922). Insurance maps of Norwalk, Connecticut. [Atlases--Connecticut--Norwalk--1922, Cadastral maps--Connecticut--Norwalk--1922, Fire insurance maps--Connecticut--Norwalk--1922]. https://collections.library.yale.edu/catalog/11580359.