What is the extremist ideology?
Extremism
George, John and Laird Wilcox. Nazis, Communists, Klansmen, and Others on the Fringe: Political Extremism in America Prometheus Books, 1992. (ISBN0-87975-680-2)
Himmelstein, Jerome L. All But Sleeping with the Enemy: Studying the Radical Right Up Close ASA, San Francisco: 1988
Hoffer, Eric. The True Believer: Thoughts on the Nature of Mass Movements. Various editions, first published 1951.
Schlesinger, Arthur. The Vital Center: The Politics of Freedom. Various editions, first published 1949.
Wilcox, Laird. "What Is Political Extremism", retrieved from 
