1. Center for Primary Care and Outcomes Research, Stanford University School of Medicine, Stanford, CA
2. Duke Clinical Research Institute, Duke University, Durham, NC, USA
3. Centre for Research on Inner City Health, Keenan Research Centre at the Li Ka Shing Knowledge Institute, Division of General Internal Medicine, St Michael's Hospital, Toronta, Ontario
4. Departments of Medicine and Health Policy, Evaluation and Management, University of Toronto, Toronto, Ontario, Canada
5. Department of Management Science and Engineering, Stanford University, Stanford, CA
6. VA Palo Alto Health Care System, Palo Alto, CA, USA