1. Creswell JW , Plano Clark VL . Designing and conducting mixed methods research. 3rd edn. Sage Publications, 2018.
2. Tashakkori A , Teddlie C . Handbook of mixed methods in social behavioral research. 2nd edn. Sage Publications, 2003.
3. Campbell DT , Stanley JC . Experimental and quasi-experimental designs for research. Houghton Mifflin Company, 1963: 1–88.
4. Strauss A , Corbin J . Basics of qualitative research: grounded theory procedures and techniques. Sage Publications, 1990.
5. Creswell JW , Creswell JD . Research design: qualitative, quantitative, and mixed methods approaches. 5th edn. Sage Publications, 2018.