Caricature to Comic Strip 

See: Finding Online Images Using Duke Sources - Specialized image databases owned (or sponsored) by Duke Libraries

Cartoon Research Library - Ohio State University maintains a database of cartoon/caricature

Cartoon Hub - hosted by the British Cartoon Library

Cartoon Stock -

Exhibitions

Comic Art at Princeton University

Cartoon America - Library of Congress exhibition with sources

Books

Encyclopedia of World Art. Lilly and Perkins: Reference N31 .E4833 1959