Tatiana V. Mayasova, Oksana V. Kolesova, N. N. D. E. G. G. E. V. K. «Implementation of Competency Approach in Teaching Mathematics to Primary School Children». Opción, Vol. 34, diciembre de 2019, pp. 798-1, https://produccioncientificaluz.org/index.php/opcion/article/view/30199.