The combination of methods proved to be valuable because each method had weaknesses: the literature search did not cover all countries; the questionnaire survey did not provide the same amount or quality of information for all countries; and the limited resources did not allow for expert interviews in all countries. Each method provided certain information that was not available from the other sources. Limitations exist for the direct comparison of single countries because of the limited number of interviews and respondents to the survey. It should be noted that the study, did not give detailed information on individual.
