@article {papaioannou2004design,
	title = {Design of a charging and accounting architecture for QoS-differentiated VPN services to mobile users},
	journal = {Computer Communications},
	volume = {27},
	number = {4},
	year = {2004},
	pages = {364{\textendash}373},
	publisher = {Elsevier},
	author = {Papaioannou, Thanasis G and Stamoulis, George D}
}
