Dr. Robert C. Worstell, Dorothea Brande, Eark Nightingale, Claude M. Bristol, Napoleon Hill (2017). “Mindset StackingTM Inspirational Journal VolumeSS02”, p.6, Lulu.com
Dr. Robert C. Worstell, Dorothea Brande, Claude M. Bristol, Earl Nightingale, Napoleon Hill (2017). “Mindset StackingTM Inspirational Journal VolumeSS01”, p.122, Lulu.com
Dr. Robert C. Worstell, James Breckenridge Jones, Napoleon Hill (2015). “Think and Grow Rich, Updated and Complete - With If You Can Count to Four...”, p.120, Lulu.com
"How to Make Money With Real Estate Options: Low-Cost, Low-Risk, High-Profit Strategies for Controlling Undervalued Property....Without the Burdens of Ownership!". Book by Thomas Lucier, 2005.
Dr. Robert C. Worstell, Dorothea Brande, Eark Nightingale, Claude M. Bristol, Napoleon Hill (2017). “Mindset StackingTM Inspirational Journal VolumeSS02”, p.150, Lulu.com