Westland, C., andj. Knight. Playing, Living, Learning: A Worldwide Perspective on Children's Opportunities to Play. State College, Pennsylvania: Venture Publishing, 1982.
Wilson, Edward O. Biophilia. Cambridge, MA: Harvard University Press, 1986.
Westland, C., andj. Knight. Playing, Living, Learning: A Worldwide Perspective on Children's Opportunities to Play. State College, Pennsylvania: Venture Publishing, 1982.
Wilson, Edward O. Biophilia. Cambridge, MA: Harvard University Press, 1986.