1. Mosher WD, Jones J. Use of contraception in the United States: 1982–2008. Vital Health Stat. 2010; 23: 1–44.
2. Lader D. Contraception and sexual health, 2008–9. London (UK): Office for National Statistics; 2009. Available: www.ons.gov.uk/ons/rel/lifestyles/contraception-and-sexual-health/2008–09/index.html.
3. Black A, Yang Q, Wu Wen S, et al. Contraceptive use among Canadian women of reproductive age: results of a national survey. J Obstet Gynaecol Can. 2009; 31: 627–640.
4. United Nations, Department of Economic and Social Affairs, Population Division (2015). Trends in Contraceptive Use Worldwide 2015 (ST/ ESA/SER. A/349). Available at www.un.org/en/development/desa/population/publications/pdffamily/trendscontraceptiveuse2015report.pdf.
5. Johns Hopkins Bloomberg School of Public Health/Center for Communication Programs and World Health Organization. Family planning: a global handbook for providers. Geneva (Switzerland): World Health Organization; 2011.