1. Kaiser Permanente Center for Health Research Portland OR USA
2. Department of Epidemiology and Environmental Health University at Buffalo, State University of New York Buffalo NY USA
3. Department of Epidemiology, Graduate School of Public Health University of Pittsburgh Pittsburgh PA USA
4. Stanford University School of Medicine Stanford University Stanford CA USA
5. Department of Obstetrics and Gynecology University of North Carolina School of Medicine Chapel Hill NC USA
6. Division of Internal Medicine, College of Medicine The Ohio State University Columbus OH USA
7. Department of Ophthalmology and Visual Sciences University of Michigan Ann Arbor MI USA
8. Department of Internal Medicine David Geffen School of Medicine at University of California, Los Angeles Division of General Internal Medicine and Health Services Research Los Angeles CA USA