Doc Lew Childre, Bruce Cryer (1998). “Freeze-frame: One Minute Stress Management : a Scientifically Proven Technique for Clear Decision Making and Improved Health”, p.6, HeartMath
Arnold Schwarzenegger (2012). “The New Encyclopedia of Modern Bodybuilding: The Bible of Bodybuilding, Fully Updated and Revis”, p.413, Simon and Schuster