* Jerry Kunzman: 'Duke was one of a kind and, like the other 'greats of yesteryear', can never be replaced. But his words and teachings can live forever in his writings."
* Rick Alemany: 'We were all fortunate to have known Duke. He was way ahead of his time and it was a great loss to the Martial Arts world when he passed."
* James Moses: 'This text teaches meditation as a skill that can be learned, taught, practiced, and mastered."
* Ferol Arce: 'Duke always had a twinkle in his eyes, and always made you feel as though you were on the right track with what ever you were trying to accomplish."