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Dyfyniad Arddull ChicagoRamage, Janet. Energy: A Guidebook. 2nd ed. New York: Oxford University Press, 1997.
Dyfyniad MLARamage, Janet. Energy: A Guidebook. 2nd ed. New York: Oxford University Press, 1997.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.