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Dyfyniad Arddull ChicagoFAO. FAO Soils Bulletin N.65: Status of Cadmium, Lead, Cobalt and Selenium in Soils and Plants of Thirty Countries. Rome: FAO, 1992.
Dyfyniad MLAFAO. FAO Soils Bulletin N.65: Status of Cadmium, Lead, Cobalt and Selenium in Soils and Plants of Thirty Countries. Rome: FAO, 1992.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.