Sources:
Brown, R. A First Language: The Early Stages. Cambridge, MA: Harvard Universtiy Press, 1973.
Erneling, Christina E. Understanding Language Acquisition. The Framework of Learning. New York: State University of New York Press, 1993.
Lindsford, Judith Wells. Children’s Language and Learning. 2nd ed. Englewood Cliffs, N.J. : Prentice-Hall, c1987.
Wanner, E. and L. Gleitman, eds. Language Acquisition: The State of the Art. Cambridge: cambridge University Press, 1982.