BOVET, M. C. (1974) "Cognitive processes among illiterate children and adults," in J. W. Berry and P. R. Dasen (eds.) Culture and Cognition: Readings in Cross-Cultural Psychology. London: Menthuen.
2.
GREENFIELD, P. M. (1966) "On culture and conservation," in J. S. Bruner, R. R. Olver, and P. M. Greenfield, et al. Studies in Cognitive Growth. New York: Johni Wiley.