[1
]
Department of Epidemiology, Graduate School of Public Health, University of Pittsburgh,
PA, USA alr143@pitt.edu.
[2
]
Department of Epidemiology and Biostatistics, School of Public Health, Drexel University,
Philadelphia, PA, USA.
[3
]
Geographic Information Systems and Spatial Analysis Laboratory, College of Information
Science and Technology, Drexel University, Philadelphia, PA, USA.