1. Bogdan R., Biklen S.: Qualitative research for education. Allyn and Bacon, Bonton (1982)
2. Cresswell J.W.: Qualitative inquiry and research design choosing among five traditions. Sage, London (1998)
3. Denzin N.K., Lincoln Y.S.: Handbook of qualitative research. Sage Publications, Thousand Oaks (1994)
4. Holsti O.R.: Content analysis for the social sciences and humanities. Addison-Wesley, Reading (1969)
5. Kuh, G.D.: Assessing what really matters to student learning. Change, 33(3), 10–17, 66 (2001)