1. 1. U.S. Department of Health and Human Services. Vital and Health Statistics: Use of Dietary Supplements in the United States 1988-1994. Hyattsville MD: U.S. Department of Health and Human Services; 1999. DHHS Publication No. 99-1694.
2. 2. Muth MK Anderson DW Domanico JL et al. Economic Characterization of the Dietary Supplement Industry: Final Report. Washington DC: U.S. Food and Drug Administration Center for Food Safety and Applied Nutrition; 1999. Contact No. 223-96-2290. Task Order 3.
3. 3. Johnston BA. One-third of the nation's adults use herbal remedies: market estimated at $3.24 billion. HerbalGram. 1997;40:49.
4. 4. Wade Q Kronenberg F Kelly A Murphy PA. Hormonemodulating herbs: implications for women's health. J Am Med Womens Assoc. 1999;54:181-183.
5. 5. Schulz V Hansel R Tyler VE. Rational Phytotherapy: A Physician's Guide to Herbal Medicine. New York: Springer; 1998.