1. Sharpe, G.B.: Travel to commercial centers in the Washington DC, metropolitan area. Bulletin 79 Highway Research Board, Washington DC (1953)
2. Voorhees, A.M., Sharpe, G.B., Stegmaier, J.T.: Shopping habits and travel patterns. Special report 11-B, Highway Research Board, Washington DC (1955)
3. Voorhees, A.M.: Basic characteristics of work trips. Thesis, Bureau of Highway Traffic, Yale University, May (1955)
4. Wynn, F.H.: Intra-city traffic movements. Paper presented at the annual meeting of Highway Research Board, Washington DC (1955)