Nikolay N. Reutov, Viktoriya V. Chirkova, I. E. R. T. P. B. T. A. S. “Social Sphere Development Regularities in Regional Reproduction in Russia”. Opción, Vol. 35, Oct. 2019, pp. 76-86, https://mail.produccioncientificaluz.org/index.php/opcion/article/view/29431.