Martin, J. A.; Hamilton, B. E.; Ventura, S. J.; et al. (November 3, 2011). "Births: Final Data for 2009"(PDF). National Vital Statistics Reports. 60 (1). Hyattsville, Maryland: National Center for Health Statistics: 1–70. PMID22670489.
Hamilton, B. E.; Martin, J. A.; Ventura, S. J. (November 17, 2011). "Births: Final Data for 2010"(PDF). National Vital Statistics Reports. 60 (2). Hyattsville, Maryland: National Center for Health Statistics.
Martin, J. A.; Hamilton, B. E.; Ventura, S. J.; et al. (November 3, 2011). "Births: Final Data for 2009"(PDF). National Vital Statistics Reports. 60 (1). Hyattsville, Maryland: National Center for Health Statistics: 1–70. PMID22670489.