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Dyfyniad Arddull ChicagoLal, Rattan. Soil Quality and Soil Erosion. Boca Raton: CRC Press, 1999.
Dyfyniad MLALal, Rattan. Soil Quality and Soil Erosion. CRC Press, 1999.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.