1. Center for Health Services Research, Department of Family Medicine, The Larner College of Medicine, University of Vermont, Burlington
2. Department of Emergency Medicine, Harvard Medical School, Boston, Massachusetts
3. Massachusetts General Hospital, Boston
4. Department of Neurology, Harvard Medical School, Boston, Massachusetts
5. Rand Corporation, Arlington, Virginia
6. Department of Health Care Policy, Harvard Medical School, Boston, Massachusetts
7. Beth Israel Deaconess Medical Center, Boston, Massachusetts