7Shim S K, Herwig J E, Shelley M. Preschoolers' play behaviors with peers in classroom and playground settings [J] . Journal of Research in Childhood Education, 2001(2).
8Tizard B, Philips J, Plewis I. Effect on play of the child's social class and of the educational orientation of the centre [J] . Journal of Child Psychology and Psychiatry, 1976(10).
9Smith P K, Connolly K. The Ecology of Pre- School Behaviour [ M]. Cambridge: Cambridge Univer-sity Press, 1983.
10Blatchford. Play time in the Primary School: Problems and hnprovement [M]. Windsor: NFER-Nelson, 1989.
