George Catlin (1841). “The Manners, Customs, and Condition of the North-American Indians, by Geo. Catlin: With Four Hundred Illustrations, Etched and Outlined, from His Original Paintings Now Exhibiting in His Indian Museum, Egyptian Hall, London”, p.46
William Shakespeare (2009). “Three Early Comedies: Love's Labor's Lost, The Two Gentlemen of Verona, The Merry Wives of Windsor”, p.86, Bantam Classics
W. Edwards Deming, Joyce (edited by) Orsini, Diana (edited by) Deming Cahill (2012). “The Essential Deming: Leadership Principles from the Father of Quality”, p.17, McGraw Hill Professional