1. Let's Create - Activities and a Philosophy for Creative Teaching;Bell,1972
2. Inexpensive Equipment for Games, Play, and Physical Activity;Corbin,1972
3. Developing Understanding of Self and Others: Play Kit and Manual;Dinkmeyer,1970
4. The development of motor skills and social relationships among primates through play;Dolhinow,1970
5. The meaning of play;Erikson,1964