1. Department of Emergency Medicine, Hennepin County Medical Center, and Department of Emergency Medicine, School of Medicine, University of Minnesota, Minneapolis, Minnesota 55455, United States
2. Department of Statistics, College of Literature, Science and Art, University of Michigan and the Informatics Institute University of Florida, Gainesville, Flordia 32611, United States
3. Emergency Medicine, University of Mississippi Medical Center, Jackson, Mississippi 39216, United States