1. Boriss, H.; Kreith, M.Spinach Profile;Agricultural Marketing Resource Center, Iowa State University:Ames, IA, 2011; http://www.agmrc.org/commodities__products/vegetables/spinach_profile.cfm(accessed Aug 17, 2011) .
2. Economic Research Service, United States Department of Agriculture (USDA). Fresh-Market Spinach: Background Information and Statistics;USDA:Washington, D.C., 2007; http://www.ers.usda.gov/News/spinachcoverage.htm(accessed Nov 14, 2008) .
3. Agricultural Research Service, United States Department of Agriculture (USDA). USDA Database for the Flavonoid Content of Selected Foods;USDA:Washington, D.C., 2003; http://www.nal.usda.gov/fnic/foodcomp/Data/Flav/flav.pdf(accessed May 21, 2007) .
4. A survey of nitrate and oxalate content in fresh vegetables