1. Husen, T. (ed.):International Study of Achievement in Mathematics. A Comparison of Twelve Countries. Stockholm/New York: Almqvist and Wicksell/John Wiley, 1967, Vol. II, p. 289.
2. Choppin, B.: ?Social Class and Educational Achievement,?Educational Research, Vol. 10, No. 3, June 1968, pp. 213?217.
3. The School in Society. The report of the Committee set up to investigate the role of the school in society. Hobart/Tasmania: Education Department, 1968.