1. Department of Emergency Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia
2. Center for Emergency Care Policy and Research, Perelman School of Medicine, University of Pennsylvania, Philadelphia
3. Department of Epidemiology, School of Public Health, School of Criminal Justice, Rutgers University, Newark, New Jersey
4. Northern Research Station, Forest Service, US Department of Agriculture, Philadelphia, Pennsylvania
5. Department of Criminology, School of Arts and Sciences, University of Pennsylvania, Philadelphia
6. Department of Epidemiology, Mailman School of Public Health, Columbia University, New York, New York
7. Department of Biostatistics and Epidemiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia