1. Bodrova, E. & Leong, D. J. (1996). Tools of the mind: The Vygotskian approach to early childhood education. Englewood Cliffs, NJ: Merrill/ Prentice Hall.
2. Bodrova, E. & Leong, D. J. (2003). Learning and development of preschool children from the Vygotskian perspective. In A. Kozulin, B. Gindis, V. Ageyev, & S. Miller (Eds.), Vygotsky's educational theory in cultural context (pp. 156-176). New York: Cambridge University Press.
3. Elkonin, D. (1977). Toward the problem of stages in the mental development of the child. In M. Cole (Ed.), Soviet developmental psychology (pp. 538-563 ). White Plains, NY: M. E. Sharpe. (Original work published 1971)
4. Elkonin, D. (1978). Psychologija igry [The psychology of play]. Moscow, Russia: Pedagogika.
5. THE PSYCHOLOGY OF PLAY