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Dyfyniad Arddull ChicagoWorld Health Organisation. WHO Expert Committee on Drug Dependence. Geneva: World Health Organisation, 1989.
Dyfyniad MLAWorld Health Organisation. WHO Expert Committee on Drug Dependence. World Health Organisation, 1989.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.