1. AAA (American Automobile Association) (1993) Your Driving Costs. Runzheimer International, Rochester, WI.
2. Alternative formulations of the Federal Highway Administration’s bid price index for highway construction;Boske;Logistics and Transportation Review,1988
3. Bureau of Census (1993) The Statistical Abstract of the United States. Bureau of Census, Washington DC.
4. Bureau of Labor Statistics (1995) State and industry average annual pay of 1993 and 1994. Press Release of Government Salaries, 19 September. BLS, Washington, DC.
5. California Air Resources Board (1991) Methodology to Calculate Emission Factors for On-Road Motor Vehicles. CARB, Sacramento, CA.