1. Mayo Clinic, Rochester, MN, USA
2. University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
3. Stanford University School of Medicine, Palo Alto, CA, USA
4. VA Palo Alto Health Care System, Palo Alto, CA, USA
5. VA Palo Alto Health Care System, Menlo Park, CA, USA
6. University of California, San Francisco, CA, USA