1. Bock, R. D., 1975. Multivariate Statistical Methods in Behavioral Research. New York: McGraw-Hill.
2. Brög, W. & E. Ampt, 1982. State of the Art in the Collection of Travel Behavior Data. In Special Report 201: Travel Analysis Methods for the 1980s. Washington, D.C.: National Research Council.
3. Brög, W. & A. H. Meyburg, 1980. The Non-Response Problem in Travel Surveys: An Empirical Investigation. Transportation Research Record No. 775, pp. 34?38.
4. Brög, W. & A. H. Meyburg, 1981. Consideration of Non-Response Effects in Large-Scale Mobility Surveys. Transportation Research Record No. 807, pp. 39?46.
5. Clarke, M., M. Dix & P. Jones, 1981. Error and Uncertainty in Travel Surveys. Transportation, 10: pp. 105?126.