World Health Organization. (2011). World health statistics 2011. World Health Organization.
Cita Chicago (17th ed.)World Health Organization. World Health Statistics 2011. Geneva, Switzerland: World Health Organization, 2011.
Cita MLA (8th ed.)World Health Organization. World Health Statistics 2011. World Health Organization, 2011.
Atenció: Aquestes cites poden no estar 100% correctes.