1. Perkins, D.N., and Salomon, G. (1999). International Encyclopedia of Education, Pergamon Press. [2nd ed.].
2. Relational understanding and instrumental understanding;Skemp;Arith. Teach.,1978
3. di Sessa, A.A., and Wagner, J.F. (2005). Transfer of Learning from a Multidisciplinary Perspective, Information Age Publishing.
4. Transfer in Pieces;Wagner;Cogn. Instr.,2006
5. Baroody, A.J. (2003). The Development of Adaptive Expertise and Flexibility: The Integration of Conceptual and Procedural Knowledge, Erlbaum.