2Valarie A. Zeithaml ,Leonard L. Berry and Parasuraman, A.():The Nature and Determinants of customer Expectations of Service. Working Paper, Report.1991, No. 91-113(May), Cambridge, Massachusetts: Marketing Science Institute.
3Christian Gronroos.Strategic Management and Marketing in the Service Sector. Research Reports. 1982,No.8, Swedish School of Economics and Business Administration, Helsinki.
4Parasuraman, A., Valarie A. Zeithaml and Leonard L. Berry.An Empirical Examination of Relationships in An Extended Service Quality Model. Report 1990,No. 90-122(December). Cambridge, Massachusetts: Marketing Science Institute.
5Parasuraman, A., Leonard L. Berry and Valarie A. Zeithaml:Refinement and Reassessment of the SERVQUAL Scale. Journal of Retailing, 1991,Volume 67, No.4(Winter),420-450.