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Dyfyniad Arddull ChicagoTechnological Substitution: Forecasting Techniques and Applications. New York: Elsevier Pub. Co, 1976.
Dyfyniad MLATechnological Substitution: Forecasting Techniques and Applications. New York: Elsevier Pub. Co, 1976.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.