Don Richard Riso, Russ Hudson (1999). “The Wisdom of the Enneagram: The Complete Guide to Psychological and Spiritual Growth for the Nine Personality Types”, Bantam
"Joan Rivers on tour: Her bitchiest putdowns and funniest one-liner jokes as she prepares for Royal Albert Hall gig" by Steve Anglesey, www.mirror.co.uk. October 09, 2012.