4WHO. World Health Statistics 2009. [2009-07-29]. Available from: URL: http://www.who.int/whosislwhostat/20091en/index.html.
5United Nations, Department of Economic and Social Affairs, Population Division. World contraceptive use 2007. [2009-07-29]. Available from URL:http://www.un.org/esa/population/publications/ contraceptive2007/contraceptive2007.htm.
6d'Arcangues C. Worldwide use of intrauterine devices for contraception. Contraception, 2007, 75(Suppl 6): S2-7.
7RHL. The WHO Reproductive Health Library: About RHL. [2009-07-29]. Available from: http://apps.who.int/rhl/resources/ about/en/index.html.
8POPLINE. The INFO Project: About POPLINE. [2009-09-02]. Available from: http://db.jhuccp.org/ics-wpd/popweb/aboutpl.html.
9Higgins JPT, Green S(editors). Cochrane Handbook for Systematic Reviews of Interventions Version 5.0.1[ updated September 2008]. The Cochrane Collaboration, 2008. [2009-07-29]. Available from: URL: http://www.cochrane-handbook.org/.