MLA

Sanborn Map Company, issuing body. Insurance Maps of Willimantic, Windham County, Connecticut. 1903. https://collections.library.yale.edu/catalog/11679623.

APA, 6th edition

Sanborn Map Company, issuing body. (1903). Insurance maps of Willimantic, Windham County, Connecticut. [Atlases--Connecticut--Willimantic--1903, Cadastral maps--Connecticut--Willimantic--1903, Fire insurance maps--Connecticut--Willimantic--1903]. https://collections.library.yale.edu/catalog/11679623.