KvaleS. To Validate is to Question. In: KvaleS, ed. Issues of Validity in Qualitative Research: Lund Studentlitteratur1989.
2.
TschudiF. Do Qualitative and Quantitative Methods Require Different Approaches to Validity? In: KvaleS, ed. Issues of Validity in Qualitative Research: Lund Studentlitteratur1989.