1. Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
2. University of California at San Francisco School of Medicine, San Francisco, California, USA
3. University of Michigan School of Medicine, Ann Arbor, Michigan, USA
4. University of California at Berkeley School of Public Health, Berkeley, California, USA
5. University of Southern California School of Medicine, Los Angeles, California, USA
6. University of Iowa College of Public Health, Ames, Iowa, USA
7. University of Cincinnati School of Medicine, Cincinnati, Ohio, USA
8. Columbia University College of Physicians and Surgeons, New York, New York, USA