1. Social interactions of toddlers and preschoolers in same- age and mixed age play groups;Bailey;Journal of Applied Developmental Psychology,1993
2. Ecological psychology: Concepts and methods for studying the environment of human behavior;Barker,1968
3. The playful child: Measurement of a disposition to play;Barnett;Play and Culture,1991
4. The message, “this is play.”;Bateson,1971
5. Toward a theory of play and phantasy;Bateson,1972