1. As quoted in: Antolini, F., The evolution of national accounting and new statistical information: Happiness and GDP, Can we measure it, Social Indicators Research, 129(3), 1075-1092, 2016.
2. Clark, A.E. et al, The Origins of Happiness: The Source of Well-Being Over the Life Course, Princeton University Press, 2018.
3. Kisch, Bruno, Scales and Weights: A Historical Outline, Yale University Press, 1965; Alder, Ken, The Measure of All Things, Little Brown, 2002.
4. Edgeworth, F.Y., Mathematical Psychics: An Essay on the Application of Mathematics to the Moral Sciences, Paul Rudd, 1881.
5. Hart, Hornell, Chart for Happiness, Macmillan, 1940.