1. Bandura, A. (1997). Self-efficacy: The excercise of control. New York: W. H. Freeman.
2. Barros, R. M., Silver, E. J., & Stein, R. E. K. (2009). School recess and group classroom behavior. Pediatrics, 123, 431–436. doi:10.1542/peds.2007-2825.
3. Bateson, P. P. G. (1981). Discontinuities in development and changes in the organization of play in cats. In K. Immelmann, G. Barlow, L. Petrinovich & M. Main (Eds.), Behavioral development (pp. 281–295). New York: Cambridge University Press.
4. Bateson, P. P. G. (2005). The role of play in the evolution of great apes and humans. In A. D. Pellegrini & P. K. Smith (Eds.), The nature of play: Great apes and humans (pp. 13–26). New York: Guilford.
5. Bergen, D. (1998). Play as a medium for learning and development: A handbook of theory and practice. Portsmouth: Heinemann.