Stephen R. Covey (1994). “Daily Reflections for Highly Effective People: Living THE SEVEN HABITS OF HIGHLY SUCCESSFUL PEOPLE Every Day”, p.192, Simon and Schuster
Letter to Harriot Hunt (1853), as quoted in "The Grimké Sisters from South Carolina: Pioneers for Woman's [sic] Rights and Abolition" by Gerda Lerner, Editorial Oxford University Press, (p. 241), 1998.