Cattletoday. CATTLE TODAY,INC., 1998-2005. Web. 23 May 2013. <http://www.cattletoday.com/archive/2006/May/CT485.shtml>.
​

Foodfirst. Food First/Institute for Food and Development Policy, 8 Apr. 2000. Web. 23 May 2013. <http://www.foodfirst.org/media/opeds/2000/4-greenrev.html>.
​

"Land Degradation: An Overview." Soils.usda. World Atlas of Desertification. London: Edward Arnold., n.d. Web. 23 May 2013. <http://soils.usda.gov/use/worldsoils/papers/land-degradation-overview.html>.
​

Nationalgeographic. National Geographic Society, Sept. 2008. Web. 23 May 2013. <http://ngm.nationalgeographic.com/print/2008/09/soil/mann-text>.
​

Pbs. WGBH educational foundation, 1995-2013. Web. 23 May 2013. <http://www.pbs.org/wgbh/pages/frontline/shows/meat/safe/>.