7PARK J Y, GORDON P, MOORE J E, et al. A two-step approach to estimating state-to-state commodity trade flows[J]. The Annals of Regional Science, 2008, 43(4):1033-1072.
8Bureau of Transportation Statistics, US Department of Transportation. Transportation statistical annual report 2008[R]. Washington DC: Bureau of Transportation Statistics, US Department of Transportation, 2009.
9JESSUP E, CASAVANT K L, LAWSON C T, et al. Truck trip data collection methods[R]. Washington DC: Federal Highway Administration, 2004.
10WOLF J, BONSALL P, OLIVEIRA M, et al. Review of the potential role of ' new technologies' in the national travel survey[R]. Leeds: University of Leeds, 2009.