Brown, L., Sherbenou, R.J., & Johnsen, S.K. ( 1997). Test of nonverbal intelligence (3rd ed.). Austin, TX: PRO-ED.
2.
Brown, L., Sherbenou, R.J., & Johnsen, S.K. ( 2010). Test of nonverbal intelligence (4th ed.). Austin, TX: PRO-ED.
3.
Hammill, D.D., Pearson, N.A., & Wiederholt, J.L. (2009). Comprehensive test of nonverbal intelligence (2nd ed.). Austin, TX: PRO-ED.
4.
Horn, J.L. ( 1965). Fluid and crystallized intelligence: A factor analytic and developmental study of the structure among primary mental abilities (Unpublished doctoral dissertation). University of Illinois, Champaign.
5.
Horn, J.L., & Cattell, R.B. ( 1966). Refinement and test of the theory of fluid and crystallized general intelligences. Journal of Educational Psychology, 57, 253-270.
6.
Spearman, C. ( 1904). General intelligence, objectively determined and measured . American Journal of Psychology, 15, 201-293.
