1. University of Pennsylvania School of Medicine Philadelphia
2. University of Pennsylvania School of Medicine and University of Pennsylvania Center for Clinical Epidemiology and Biostatistics Philadelphia Pennsylvania
3. University of Nebraska Medical Center Omaha
4. Salt Lake City Veteran Affairs Medical Center and University of Utah Salt Lake City Utah
5. University of Pennsylvania School of Medicine, University of Pennsylvania Center for Clinical Epidemiology and Biostatistcs, and Corporal Michael J. Crescenz Veterans Affairs Medical Center Philadelphia Pennsylvania