World Health Organization. (1999). Sexually transmitted infections prevalence study methodology. World Health Organization.
Dyfyniad Arddull ChicagoWorld Health Organization. Sexually Transmitted Infections Prevalence Study Methodology. Geneva,Switzerland: World Health Organization, 1999.
Dyfyniad MLAWorld Health Organization. Sexually Transmitted Infections Prevalence Study Methodology. World Health Organization, 1999.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.