Gaya APA

Zeithaml, V, A. et al (1990). Delivering Quality Service: Balancing Customer Perceptions and Expectations . London: Collier Macmillan Publisher.

Gaya MLA

Zeithaml, Valerie, A.. et al. "Delivering Quality Service: Balancing Customer Perceptions and Expectations". London: Collier Macmillan Publisher, 1990. Text.