1. Barzun, J., & Graff, H. E. (1977). The modern researcher (3rd ed.). Harcourt Brace Jovanovich.
2. Baumeister, R., & Tierney, J. (2011). Willpower: Rediscovering our greatest strength. Allen Lane.
3. Blaxter, L., Hughes, C., & Tight, M. (2010). How to research (4th ed.). The Open University and McGraw-Hill Education.
4. Braun, V., & Clarke, V. (2013). Successful qualitative research: A practical guide for beginners. Sage.
5. Burns, E. B. (2000). Introduction to research methods. Sage Publications.