1. Anderson LW, Krathwohl DR (2001) A taxonomy for learning, teaching, and assessing: a revision of bloom’s taxonomy of educational objectives. Longman, New York
2. Bratthall L, Jorgensen M (2002) Can you trust a single data source exploratory software engineering case study. J Empir Softw Eng 7:9–26
3. Brewer J, Hunter A (1989) Multi-method research: a synthesis of styles. Sage, Newbury
4. Campbell DT, Stanley JC (1963) Experimental and quasi-experimental designs for research. Houghton Mifflin, Boston, MA
5. Cresswell JW (2002) Research design: qualitative, quantitative and mixed method approaches. Sage, Newbury