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.100, 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.85, Lulu.com