Theodore Roosevelt (2015). “Theodore Roosevelt on Bravery: Lessons from the Most Courageous Leader of the Twentieth Century”, p.13, Skyhorse Publishing, Inc.
Dr. Robert C. Worstell, Dorothea Brande, Eark Nightingale, Claude M. Bristol, Napoleon Hill (2017). “Mindset StackingTM Inspirational Journal VolumeSS02”, p.38, Lulu.com
Booker T. Washington (1901). “An Autobiography: The Story of My Life and Work, the Original Brought Up-to-date with Over Half a Hundred Full Page Photo and Halftone Engravings and Drawings by Frank Beard”