Kosaretsky, Sergey, Boris Kupriyanov, and Filippova Darya. 2016. “Specific Features of Children Involvement in Supplementary Education Depending on Cultural, Educational and Financial Status of Families and Place of Living”. Voprosy Obrazovaniya / Educational Studies Moscow, no. 1 (March), 168-90. https://doi.org/10.17323/1814-9545-2016-1-168-190.