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Dyfyniad Arddull ChicagoEconomy, Peter. Customer Service Secrets. New Delhi: Tata McGraw-Hill Publishing Company Ltd, 2004.
Dyfyniad MLAEconomy, Peter. Customer Service Secrets. New Delhi: Tata McGraw-Hill Publishing Company Ltd, 2004.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.