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2. US Department of Agriculture, Agricultural Research Service. USDA Food and Nutrient Database for Dietary Studies. Available at: http://www.ars.usda.gov/Services/docs.htm?docid=7673. Accessed October 26, 2006.
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4. Use of dietary supplements in the United States, 1988-94;Ervin;Vital Health Stat 11,1999
5. Food and dietary supplement databases for What We Eat in America-NHANES;Dwyer;J Nutr,2003