1. Bouchard, T., and McGue, M. (1981). Familial studies of intelligence. A review.Science 212:1055?1059.
2. Cohen, J. (1957). The factorial structure of the WAIS between early adulthood and old age.J. Consult. Psychol. 21:283?290.
3. Engvik, H. (1978). Faktorstrukturen i WAIS. Unpublished paper, Institute of Psychology, University of Oslo, Oslo.
4. Engvik, H., Hjerkin, O., and Seim, S. (1978).Manual for WAIS, Norwegian version, Oslo.
5. Jøreskog, K. G. (1973). Analysis of covariance structures. In Krishnaiah, P. R. (ed.),Multivariate Analysis III, Academic Press, New York.