Dr. Robert C. Worstell, Dorothea Brande, Claude M. Bristol, Earl Nightingale, Napoleon Hill (2017). “Mindset StackingTM Inspirational Journal VolumeSS01”, p.140, Lulu.com
Jane Austen (2013). “Jane Austen Collection: Pride and Prejudice, Sense and Sensibility, Mansfield Park, Emma, Persuasion, Northanger Abbey, Lady Susan, Love and Friendship and Other Austin Works”, p.700, Lulu Press, Inc
Richard P. Feynman (2010). “"Surely You're Joking, Mr. Feynman!": Adventures of a Curious Character: Adventures of a Curious Character”, p.346, W. W. Norton & Company