Frost, J. L., Wortham, S. C., & Reifel, R. S. (2001). Play and child development. Merrill, Prentice Hall.
Lua i Stíl Chicago (17ú heag.)Frost, Joe L., Sue Clark Wortham, agus Robert Stuart Reifel. Play and Child Development. Upper Saddle River, N.J: Merrill, Prentice Hall, 2001.
Lua MLA (9ú heag.)Frost, Joe L., et al. Play and Child Development. Merrill, Prentice Hall, 2001.
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