1. World Bank (2013) World development indicators. Available at databank.worldbank.org/data/reports.aspx?source=world-development-indicators. Accessed October 16, 2013
2. The exceptionally high life expectancy of Costa Rican nonagenarians
3. National Research Council (2011) Explaining Divergent Levels of Longevity in High-Income Countries (National Academies Press, Washington, DC)
4. National Research Council (2011) International Differences in Mortality at Older Ages: Dimensions and Sources (National Academies Press, Washington, DC)
5. National Research Council & Institute of Medicine (2013) U.S. Health in International Perspective: Shorter Lives, Poorer Health (National Academies Press, Washington, DC)