Vogels , Ton, Ron van der Vliet , Menno Danz , et al. "YOUNG PEOPLE AND SEX: BEHAVIOUR AND HEALTH RISKS IN DUTCH SCHOOL STUDENTS" International Journal of Adolescent Medicine and Health, 6.2 (2011): 137-147. Retrieved 20 Jun. 2013, from doi:10.1515/IJAMH.1993.6.2.137

Vogels , T., Vliet , R., Danz , M., et al. (2011). YOUNG PEOPLE AND SEX: BEHAVIOUR AND HEALTH RISKS IN DUTCH SCHOOL STUDENTS. International Journal of Adolescent Medicine and Health, 6(2), pp. 69-147. Retrieved 20 Jun. 2013, from doi:10.1515/IJAMH.1993.6.2.137

Vogels , Ton, Ron van der Vliet , Menno Danz , et al. 2011. YOUNG PEOPLE AND SEX: BEHAVIOUR AND HEALTH RISKS IN DUTCH SCHOOL STUDENTS. International Journal of Adolescent Medicine and Health. 6(2): 69-147. Retrieved 20 Jun. 2013, from doi:10.1515/IJAMH.1993.6.2.137