Flores Moreno, Pedro Julián, et al. “The Effective Time Measurement of Physical Education and Its Impact on Caloric Expenditure at Primary Schoolchildren Level Municipality of Colima, Mexico”. Sportis. Scientific Technical Journal of School Sport, Physical Education and Psychomotricity, vol. 3, no. 1, Sept. 2016, pp. 34-49, doi:10.17979/sportis.2017.3.1.1766.