Buckminster Fuller (1992). “Cosmography: A Posthumous Scenario for the Future of Humanity: A Posthumous Scenario for the Future of Humanity”, p.27, The Estate of R. Buckminster Fuller
Walt Kelly (1974). “Pogo revisited: containing the complete volumes of The Pogo poop book, Instant Pogo [and] The Jack Acid Society black book”, Simon & Schuster
Peter M. Senge, C. Otto Scharmer, Joseph Jaworski, Betty Sue Flowers (2005). “Presence: An Exploration of Profound Change in People, Organizations, and Society”, p.225, Crown Business