Charles F. Haanel, Donald Gordon Carty (2013). “The Master Key System: 2nd Edition: Open the Secret to Health, Wealth and Love, 24 Lesson Workbook”, p.122, Lulu Press, Inc
Jane Roberts, Seth (Spirit), Robert F. Butts (1994). “The Nature of Personal Reality: Specific, Practical Techniques for Solving Everyday Problems and Enriching the Life You Know”, p.436, New World Library
Charles F. Haanel, Donald Gordon Carty (2013). “The Master Key System: 2nd Edition: Open the Secret to Health, Wealth and Love, 24 Lesson Workbook”, p.122, Lulu Press, Inc
Jane Roberts, Seth (Spirit), Robert F. Butts (1994). “The Nature of Personal Reality: Specific, Practical Techniques for Solving Everyday Problems and Enriching the Life You Know”, p.436, New World Library