D. Carraher, и D. Earnest. Proceedings of the 2003 Joint Meeting of PME and PMNA (PME27 and PME-NA25), 2, стр. 173--180. 1776 University Av., Honolulu, HI 96822, International Group for the Psychology of Mathematics Education, College of Education, University of Hawai'i, (июля 2003)