1. Adolescent pregnancy and childbearing: Levels and trends in developed countries;Singh;Fam Plann Perspect,1999
2. National Campaign to Prevent Teen and Unplanned Pregnancies (2012). Teen pregnancy in the United States: Fast facts, http://www.thenationalcampaign.org/resources/pdf/FastFacts_TeenPregnancyinUS.pdf. Accessed February 13, 2013.
3. Emerging Answers 2007: Research findings on programs to reduce teen pregnancy and sexually transmitted diseases;Kirby,2007
4. Births: preliminary data for 2007;Hamilton;Natl Vital Stat Rep,2009
5. U.S. teenage pregnancies, births, and abortions: National and state trends and trends by race and ethnicity,2010