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Dyfyniad Arddull ChicagoFichter, Lynn S., and G. Thomas Farmer. Earth Materials and Earth Processes: An Introduction. 3rd ed. New York: Macmillan, 1991.
Dyfyniad MLAFichter, Lynn S., and G. Thomas Farmer. Earth Materials and Earth Processes: An Introduction. 3rd ed. Macmillan, 1991.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.