1. Northern California Kaiser-Permanente Division of Research, Oakland and Departments of Medicine and Epidemiology and Biostatistics, University of California, San Francisco, San Francisco, California
2. Department of Biostatistics, University of Arkansas for Medical Sciences, Little Rock, Arkansas
3. National Center for Complementary and Alternative Medicine, National Institutes of Health, Bethesda, Maryland
4. General Medicine Division, Massachusetts General Hospital, Boston, Massachusetts