1. The Guttmacher Institute. (2006). U.S. teenage pregnancy statistics national and state trends and trends by race and ethnicity. New York: The Guttmacher Institute.
2. Martin, J. A., Hamilton, B. E., Sutton, P. D., & Ventura, S. J., et al. (2009). Births: Final data for 2006. National vital statistics reports, (Vol. 57, no. 7). Hyattsville, MD: National Center for Health Statistics.
3. National Campaign to Prevent Teen and Unplanned Pregnancy. (2007). By the numbers. http://www.teenpregnancy.org/costs/default_oct27.asp . Accessed 6 Nov 2007.
4. Landry, D. J., & Forrest, J. D. (1995). How old are U.S. fathers? Family Planning Perspectives, 27, 159–161. see also 165.
5. Males, M., & Chew, K. S. (1996). The ages of fathers in California adolescent births, 1993. American Journal of Public Health, 86, 565–568.