1. Guyer, B., Freedman, M. A., Strobion, D. M., & Sondick, E. J. (2000). Annual summary of vital statistics: Trends in the health of Americans during the 20th century. Pediatrics, 106(6), 1307–1317. doi: 10.1542/peds.106.6.1307 .
2. Mathews, T. J., & MacDorman, M. F. (2006). Infant mortality statistics from the 2003 period linked birth/infant death data set. National Vital Statistics Reports, 54(16), 1–9.
3. Buekens, P., & Klebanoff, M. (2001). Preterm birth research, from disillusion to the search for new mechanisms. Paediatric and Perinatal Epidemiology, 15, 159–161. doi: 10.1046/j.1365-3016.2001.00015.x .
4. U.S. Department of Health, Human Services. (2000). Healthy people 2010 objectives for improving health (2nd ed.). Washington, DC: U.S. Government Printing Office.
5. U.S. Department of Health, Human Services Public Health Service. (1989). Caring for our future; the content of prenatal care (2nd ed.). Washington, DC: U.S. Government Printing Office.