Jeffrey D. Sachs, The End of Poverty: Economic Possibilities for Our Time (New York: Penguin Press, 2005).
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Tom Worstall, «Six Waltons Have More Wealth Than the Bottom 30 % of Americans», Forbes, December 14, 2011. http://www.forbes.com/sites/timworstall/2011/12/14/sixwaltons-have-more-wealth-than-the-bottom-30-of-americans/.
