1. Trends in Sexual Risk Behaviors among High School Students—United States, 1991 to 1997 and 1999 to 2003;Feijoo,2004
2. A League Table of Teenage Births in Rich Nations. Available from: http://www.unicef-icdc.org/publications/pdf/repcard3e.pdf
3. Trends in sexual risk behaviors among high school students—United States, 1991–2001;Brener;JAMA,2002
4. Sexual behavior in Britain;Wellings;Lancet,2001
5. Change over time;Rosenthal;Venereology,1998