1. C. Csikos, in Proceedings of the 23th of the International Group for the Psychology of Mathematics Education, 2, (1999), pp. 233– 240.
2. K. Reiss, Hellmich, F. and M. Reiss, PME, 26, 4-113 - 4-120 (2002).
3. R. Maya, IndoMS JME, 2 (2), pp. 231–250 (2011).
4. Lee, K., “Students’ Logical Reasoning and Mathematical Proving of Implications,” Disertasi, Michigan State University, 2011.
5. Validations of Proofs Considered as Texts: Can Undergraduates Tell Whether an Argument Proves a Theorem?