Erikson Institute, Loyola University, Chicago. Department of Psychology, Loyola University, Chicago. School of Education, Piaget, J., & Piers, M. W. (1972). Play and development: A symposium. Norton.
Chicago-viite (17. p.)Erikson Institute, Chicago. Department of Psychology Loyola University, Chicago. School of Education Loyola University, Jean Piaget, ja Maria W. Piers. Play and Development: A Symposium. New York: Norton, 1972.
MLA-viite (9. p.)Erikson Institute, et al. Play and Development: A Symposium. Norton, 1972.
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