1. Southern California Kaiser Permanente, Pasadena, California 91101;
2. Departments of Pediatrics and Health Services, University of California, Los Angeles, California 90095;
3. RAND, Santa Monica, California 90407;
4. Department of Health Services, University of California, Los Angeles;
5. County of Los Angeles Department of Health Services, Los Angeles, California 90012;
6. Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles;
7. Department of Medicine, University of California, Los Angeles, California 90095;