Albert Karl, & J. Bradford Lawrence. (1990). The Service Advantage: How to Identify and Fulfill Customer Needs (In lần thứ 1.). U.S.A: Dow Jones - Irwin.
Dyfyniad Arddull ChicagoAlbert Karl, và J. Bradford Lawrence. The Service Advantage: How to Identify and Fulfill Customer Needs. In lần thứ 1. U.S.A: Dow Jones - Irwin, 1990.
Dyfyniad MLAAlbert Karl, và J. Bradford Lawrence. The Service Advantage: How to Identify and Fulfill Customer Needs. In lần thứ 1. U.S.A: Dow Jones - Irwin, 1990.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.