True Colors, Roger Birkman, Ph.D., Thomas Nelson Publishers, 1995

Quality is Personal, Harry Roberts and Bernie Sergesketter, The Free Press, 1993

Flow: The Psychology of Optimal Experience, Mihaly Csikszentmihaly, Harper Perennial, 1990

The Seven Habits of Highly Effective People, Stephen R. Covey, Simon & Schuster, 1989

How to Win Friends and Influence People, Dale Carnegie, Simon and Schuster, 1936, 1981