1. Boethius, C. G., (1974).Sex and Family Planning Education, Statens offentliga utredningar, No. 59, Utbildningsdepartementet, Stockholm. (In Swedish with English summary)
2. Central Bureau of Statistics. (1986). Statistical Yearbook of Norway, Central Bureau of Statistics, Oslo-Kongsvinger.
3. Christensen, H. T., and Gregg, C. F. (1970). Changing sex norms in America and Scandinavia.J. Marr. Fam. 32: 616?627.
4. Cox, D. R., (1972). Regression models and life tables.J. Roy. Statist. Soc. B, 34: 187?220.
5. Currie, C. (1990). Young people in independent school, sexual behaviour and AIDS. In Aggleton, P., Davies P., and Hart, G. (eds.),Individual, Cultural, and Policy Dimensions Falmer Press, London, pp. 73?87.