William Stanley Jevons (1874). “The Principles of Science: Book IV. Inductive investigation. Book V. Generalization, analogy, and classification. Book VI. Reflections on the results and limits of scientific method”, p.288
"Society: Governments must tackle record gap between rich and poor, says OECD". José Ángel Gurría's remarks during the launching of a new 2011 OECD report "Divided We Stand: Why Inequality Keeps Rising", www.oecd.org. December 5, 2011.