1. Bouchard, T. J., Jr. & Segal, N. L. (1985). IQ and environment. In B. B. Wolman (Ed.), Handbook of intelligence @p. 391-464). New York: Wiley.
2. Buss, A. H. & Plomin, R. (1984). Temperament: Early developing personality traits. Hillsdale, NJ: Lawrence Erlbaum Associates, Inc.
3. THE DEVELOPMENT OF SPEECH AND MENTAL PROCESSES IN A PAIR OF TWINS: A CASE STUDY
4. Specific cognitive abilities in 5- to 12-year-old twins