1. Ventura, S. J., Martin, J. A., Curtin, S. C., & Mathews, T. J. (1999). Births: final data for 1997. National Vital Statistics Reports, 47(18), 1–96.
2. MacDorman, M. F., & Atkinson, J. O. (1999). Infant mortality statistics from the 1997 period linked birth/infant death data set. National Vital Statistics Reports, 47(23), 1–23.
3. Wood, N. S., Marlow, N., Costeloe, K., Gibson, A. T., & Wilkenson, A. R. (2000). Neurologic and Developmental Disability after Extremely Preterm Birth, New England Journal of Medicine, 343(6), 378–384.
4. England L. Preterm Singleton Births, US. Ferre C, Martin J, & Hogan V, (Eds.) Morbidity and Mortality Weekly Report, 48(9), 185–189. 3-12-1999.
5. Centers for Disease Control and Prevention (CDC). 2000. State-specific changes in singleton preterm births among black and white women–United States, 1990 and 1997. Morbidity and Mortality Weekly Report, 49(37), 837–840.