1. Group Health Research Institute; Group Health Cooperative; Seattle WA USA
2. Health Services Research Department; LCF Research; Albuquerque NM USA
3. Meyers Primary Care Institute; Worcester MA USA
4. Pharmacy Analytical Service; Kaiser Permanente; Downey CA USA
5. Center for Drug Evaluation and Research, U. S. Food and Drug Administration; Silver Spring MD USA
6. Harvard Medical School and Harvard Pilgrim Health Care Institute; Boston MA USA
7. School of Medicine; Vanderbilt University; Nashville TN USA
8. Center for Health Research, Southeast; Kaiser Permanente; Atlanta GA USA
9. Institute for Education and Research; HealthPartners; Bloomington MN USA
10. Institute for Health Research; Kaiser Permanente Colorado; Denver CO USA
11. Center for Health Research; Northwest, Kaiser Permanente; Portland OR USA
12. Division of Research; Kaiser Permanente; Oakland CA USA