DiJulius, J. R. (2003). Secret service: Hidden systems that deliver unforgettable customer service. AMACOM.
Chicago (17e ed.) BronvermeldingDiJulius, John R. Secret Service: Hidden Systems That Deliver Unforgettable Customer Service. New York: AMACOM, 2003.
MLA (9e ed.) BronvermeldingDiJulius, John R. Secret Service: Hidden Systems That Deliver Unforgettable Customer Service. AMACOM, 2003.
Let op: Deze citaties zijn niet altijd 100% accuraat.