1. Valarie A. Zeithaml , A. Parasuraman and Leonard L. Berry, Delivering Quality Service: Balancing Customer Perceptions and Expectations. New York: The Free Press, 1990. 16.
2. A. Parasuraman. "The SERVQUAL Model: Its Evolution and Current Status." Presentation: ARL Symposium on Measuring Service Quality. Washington, DC: October 20, 2000. Available Saturday, April 28, 2001 at: http://www.arl.org/libqual/events/oct2000msq/slides/parasuraman/sld001.htm; Leonard Berry. On Great Service: A Framework for Action . New York: The Free Press, 1995. 35.
3. Measuring service quality at yale university’s libraries