MLA

Sanborn Map Company, issuing body. Unionville, Hartford County, Connecticut. 1921. https://collections.library.yale.edu/catalog/11675409.

APA, 6th edition

Sanborn Map Company, issuing body. (1921). Unionville, Hartford County, Connecticut. [Atlases--Connecticut--Avon--1921, Atlases--Connecticut--Unionville--1921, Cadastral maps--Connecticut--Avon--1921, Cadastral maps--Connecticut--Unionville--1921, Fire insurance maps--Connecticut--Avon--1921, Fire insurance maps--Connecticut--Unionville--1921]. https://collections.library.yale.edu/catalog/11675409.