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Dyfyniad Arddull ChicagoMETCALF,EDDY. WESTE WATER ENGG. TREATMENT DISPOSAL REFUSAL. TMH, 1979.
Dyfyniad MLAMETCALF,EDDY. WESTE WATER ENGG. TREATMENT DISPOSAL REFUSAL. TMH, 1979.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.