Marani, F., A. R. de Oliveira, and M. K. Omori. “Physical Activity in Adolescents of Different Social Economic Levels”. Journal of Physical Education (Maringá), Vol. 16, no. 1, May 2008, pp. 67-71, https://periodicos.uem.br/ojs/index.php/RevEducFis/article/view/3405.