1. Animals at play;Brown S. L.;National Geographic,1994
2. Play and Therapeutic Action
3. Eddington, A. 1927. Stars and atoms. New Haven: Yale University Press.
4. Ferenczi, S. 1933. The confusion of tongues between adults and the child. In Final contributions to the problems and methods of psycho-analysis, ed. M. Balint, 156–67. (NY): Bruner/Mazel, 1955.
5. The play's the thing how the essential processes of therapy are seen most clearly in child therapy