1. Transportation SystemAnalysis Model, Blacksburg,Virginia, May2005.
2. 2: U.S. Census Bureau, Census 2000 population file, http://www2.census.gov/census_2000/datasets/redistricting_file-pl_94-171/
3. 3: U.S. Census Bureau, Census TIGER 2000/Line file, http://www.esri.com/data/download/census2000_tigerline/
4. 5:FederalAviationAdministration,General Aviationand Air Taxi Activity Survey, Washington DC.2002.