1. World Water Distribution, EPA, http://www.epa.gov/seahome/groundwater/
2. Freshwater resources and withdrawals, World Resources Institute, 2001, http://www.wri.org/
3. International year of freshwater 2003, United Nations, http://www.wateryear2003.org/
4. World Population Information, U.S. Census Bureau, http://www.census.gov/ipc/www/world.html
5. Population Reference Bureau, http://www.prb.org/