Florence Scovel Shinn, Laura Berman Fortgang (2015). “The Complete Game of Life and How to Play It: The Classic Text with Commentary, Study Questions, Action Items, and Much More”, p.15, Hampton Roads Publishing
Robin Sharma (2006). “The Greatness Guide: One of the World's Most Successful Coaches Shares His Secrets for Personal and Business Mastery”, p.20, Jaico Publishing House