"Exclusive Interview: Alexander 'The Mauler' Gustafsson – What Karate Can Learn from MMA". Interview with Jesse Enkamp, www.karatebyjesse.com. April 11, 2013.
Ernest Holmes, Michael Beckwith (2010). “How to Change Your Life: An Inspirational, Life-Changing Classic from the Ernest Holmes Library”, p.2, Health Communications, Inc.