1. Department of Health Behavior and Health Education University of Michigan School of Public Health Ann Arbor Michigan USA
2. Department of Biostatistics and Epidemiology Rutgers School of Public Health Piscataway New Jersey USA
3. USDA Forest Service, Northern Research Station Philadelphia Pennsylvania USA
4. Department of Emergency Medicine University of Michigan Medical School Ann Arbor Michigan USA
5. Department of Epidemiology Columbia Mailman School of Public Health New York New York USA
6. Division of Violence Prevention, National Center for Injury Prevention and Control, Centers for Disease Control and Prevention Atlanta Georgia USA