1. US Bureau of the Census. Percent of people 25 years and over who have completed high school or college, by race, Hispanic origin and sex: selected years 1940 to 2004 (noninstitutionalized population). 2005. Available at: http://www.census.gov/population/socdemo/education/tabA-2.pdf. Accessed December 29, 2006.
2. Declining estimates of infertility in the United States: 1982-2002;Stephen;Fertil Steril,2006
3. Mean age of mother, 1970-2000;Mathews;Natl Vital Stat Rep,2002
4. Revised birth and fertility rates for the United States, 2000 and 2001;Ventura;Natl Vital Stat Rep,2003
5. Births: final data from 2000;Martin;Natl Vital Stat Rep,2002