D. Carraher, A. Schliemann, and B. Brizuela. Proceedings of the XXV Conference of the International Group for the Psychology of Mathematics Education, (2001)
J. DeLoache. Child Psychology in Retrospect and Prospect: In Celebration of the 75th Anniversary of the Institute of Child Development, Lawrence Erlbaum Associates, Mahwah, NJ, (2002)
J. Smith, and P. Thompson. Employing children's natural powers to build algebraic reasoning in the context of elementary mathematics, Erlbaum, New York, (2007)