1. Lomborg, B. The Skeptical Environmentalist: Measuring the Real State of the World (Cambridge Univ. Press, 2001).
2. Keyfitz, N. & Flieger, W. World Population Growth and Aging Vol. 107 (Univ. Chicago Press, 1990).
3. Lutz, W., Sanderson, W. & Scherbov, S. Doubling of world population unlikely. Nature 387, 803–805 (1997).
4. Russell, J. C. in Fontana Economic History of Europe Vol. 1 (ed. Cipolla, C.) 25–70 (Fontana, London, 1978).
5. La Croix, A. Z., Lipson, S., Miles, T. P. & Whilte, L. Prospective study of pneumonia hospitalization and mortality of U.S. older people: the role of chronic conditions, health behaviours and nutritional status. Public Health Rep. 104, 350–360 (1989).