Μπλέρη Ε., and Μιχαλακοπούλου Μ. “CRM (customer Relationship Management) Applications in the Greek Mobile Telephony Companies: A Comparative Analysis”. SPOUDAI Journal of Economics and Business, vol. 56, no. 3, Aug. 2006, pp. 71-94, http://spoudai.org/index.php/journal/article/view/375.