1. T. R. Malthus, An Essay on the Principle of Population (John Murray, London, ed. 6, 1826).
2. P. R. Ehrlich, The Population Bomb (Ballantine Books, New York, 1968).
3. United Nations (UN), Department of Economic and Social Affairs, Population Division, “World Population Prospects: The 2015 Revision” (Working Paper no. ESA/P/WP 241, UN, 2015).
4. D. H. Meadows, D. L. Meadows, J. Randers, W. W. Behrens III, The Limits to Growth (Universe Books, New York, 1972).
5. Planetary Boundaries: Exploring the Safe Operating Space for Humanity