1. National Center for Complementary and Alternative Medicine. Expanding Horizons of Healthcare: Five-Year Strategic Plan 2001–2005 (National Institutes of Health, Bethesda, 2000).
2. Ernst, E. Prevalence of use of complementary/alternative medicine: a systematic review. Bull. World Health Organ. 78, 252–257 (2000).
3. Barnes, P. M., Powell-Griner, E., McFann, K. & Nahin, R. L. Complementary and alternative medicine use among adults: United States, 2002. Adv. Data 343, 1–19 (2004).
4. Eisenberg, D. M. et al. Trends in alternative medicine use in the United States, 1990–1997: results of a follow-up national survey. JAMA 280, 1569–1575 (1998).
5. Ni, H., Simile, C. & Hardy, A. M. Utilization of complementary and alternative medicine by United States adults: results from the 1999 National Health Interview Survey. Med. Care 40, 353–358 (2002).