González-Giraldo, Omaira Elizabeth, and María Teresa Castellanos Sánchez. “The Abacus Closed As a Pedagogical Mediation in the Construction of Multiplication and Division Operations in the Third Degree of Official Educational Institutions”. Inclusión Y Desarrollo, vol. 6, no. 2, June 2019, pp. 98-108, doi:10.26620/uniminuto.inclusion.6.2.2019.98-108.