1. Aron, A., Aron, E.N., and Coups, E.J. (2002). Statistics for psychology. Upper Saddle River, NJ: Prentice Hall.
2. Cramer, H. (1999). Mathematical methods of statistics. Champaign: Princeton University Press.
3. Fédération Internationale de Football Association (2014). Laws of the Game: Law 3 (pp17-20). Zurich: FIFA.