Guevara Benítez, Y.; Hermosillo García, Ángela; López Hernández, A.; Delgado Sánchez, U.; García Vargas, G. R.; Rugerio Tapia, J. P. Mathematical Skills in Students from a Low Social and Cultural Stratum. Acta. Colomb. Psicol. 2008, 11, 13-24.