1. Mailed evaluation questionnaires
2. Ampt, E. (1997), “Respondent Burden: Understanding the People we Survey!” Resource paper prepared for a Workshop on the Influence of Respondent Burden for Transport Surveys: Raising the Standard, an International Conference on Transport Survey Quality and Innovation, May 24–30, 1997, Grainau, Germany.
3. Brög, W. and Neuman, K. (1977), “The Interviewee as a Human Being”, XLIV ESOMAR Seminar on “Ways and New Ways of Data Collection”, Jouy-en-Josas, France.