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Dyfyniad Arddull ChicagoTull, Donald S. Marketing Research: Measurement & Method. 6th ed. New Delhi: Prentice hall od India, 2002.
Dyfyniad MLATull, Donald S. Marketing Research: Measurement & Method. 6th ed. Prentice hall od India, 2002.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.