1. Department of Geography and Regional Development, University of Arizona, Harvill Building Box #2, 1103 East 2nd Street, Tucson AZ 85712, USA
2. Department of Geography, University of Kentucky, 1457 Patterson Office Tower, Lexington, KY 40506-0027, USA
3. Kentucky Transportation Center, 176 Raymond Building, University of Kentucky, Lexington, KY 40506, USA