1. Bates, E., 1979, The Emergence of Symbols, Cognition and Communication in Infancy, Academic Press, New York.
2. Bruner, J. S., 1974–1975, From communication to language—A psychological perspective, Cognition
3(3):255–287.
3. Bullowa, M., 1979, Introduction: Prelinguistic communication. A field for scientific research, in: Before Speech. The Beginning of Interpersonal Communication (M. Bullowa, ed.), Cambridge University Press, Cambridge pp. 1–62.
4. De Waal, F. B., and Hoekstra, J. A., 1980, Contexts and predictability of aggression in champanzees, Anim. Behav.
28:929–937.
5. Gardner, R. A., and Gardner, B. T., 1969, Teaching sign-language to chimpanzees, Science
165:664.