References
- Brown, S. (2009). Play: How it shapes the brain, opens the imagination and invigorates the soul. Avery/Penguin.
- Gray, P. (2013). Free to learn: why unleashing the instinct to play will make our children happier, more self-reliant and better students for life. Basic Books.
- Sutton-Smith, B. (1997). The ambiguity of play. Harvard University Press.