1. Fred Rogers,Mister Rogers' Playtime(Philadelphia: Running Press, 2001), 28.
2. Patricia Monighan-Nourot, Barbara Scales, Judith Van Hoorn, with Millie Almy,Looking at Children's Play: A Bridge Between Theory and Practice(New York: Teachers College Press, 1987), 15–19.
3. Sandra Smidt,Playing to Learn: The Role of Play in the Early Years(New York: Routledge, 2011), 2. Smidt references Getting Serious About Play—A Review of Children's Play (London: Department for Culture, Media and Sport, 2004).
4. Lev Vygotsky,Mind in Society(Cambridge: Harvard University Press, 1978), 102.