Agharebparast, Farshid, and Victor C. M. Leung. “A Framework for QoS Support in the UMTS GPRS Backbone Network Using DiffServ”. COMPUTING AND INFORMATICS, vol. 21, no. 2, Feb. 2012, pp. 97-118, https://www.cai.sk/ojs/index.php/cai/article/view/499.