1. M.J. Moroney. Facts From Figures. 3rd edn.. Penguin. Baltimore, MD. 1956, p. 1.
2. G. Udney Yule and M. G. Kendall. An Introduction to the Theory of Statistics, Hafner. New York. 1950. p. xvii.
3. Quoted in Harry Hopkins. The Numbers Game. Little. Brown. Boston. MA, 1973, p. 21.
4. Quoted in James H. Cassedy, Demography in Early America. Harvard University Press, Cambridge. MA, 1969. p. 105.
5. Quoted in Hopkins, op. cit., p. 23.