1. O. Aslan and Ş.U. Sağır, “Problem-Solving Skills of Science and Technology Teacher Candidates”, in Turkish Journal of Science Education, Vol. 9, No. 2, (2011), pp. 82–94.
2. NCTM, “Principles and Standars for School Mathematics”. (VA, USA, 2000).
3. G. Polya, “Mathematics and Plausible Reasoning, Volume I”. (Princeton University Press, Princeton, 1990).
4. E. Goldman, “Leadership Practices that Encourage Strategic Thinking”, in Journal of Strategy an management, Vol. 5, No. 1, (2012), pp. 25–40.
5. Validation of a short questionnaire to assess the degree of complexity and structuredness of PBL problems