Ahmad , Z., M. A. Sandhu, W. Ali, M. . Abbas, and J. Iqbal. “Understanding the Demographic Variations in Service Quality Perception: An Exploratory Study on Cellular Industry of Pakistan”. Pakistan Journal of Social Sciences, vol. 37, no. 1, June 2017, pp. 273-88, http://pjss.bzu.edu.pk/index.php/pjss/article/view/535.