Silva, A. I. da, F. N. dos Santos, and A. K. A. Brito. “Analysis of the Aerobic and Anaerobic Capacity of Brazilian Elite Soccer Referees”. Journal of Physical Education (Maringá), Vol. 19, no. 1, July 2008, pp. 77-84, https://periodicos.uem.br/ojs/index.php/RevEducFis/article/view/4317.