1. Report 21 from the UMTS Forum (2002) Charging, Billing and Payment Views on 3G Business Models, http://www.umts-forum.org/reports.
2. An integrated charging, accounting and billing management platform for the support of innovative business models in mobile networks;Koutsopoulou;Int. J. Mobile Commun.,2004
3. Charging, Accounting & Billing Management in Mobile Telecommunication Networks and the Internet;Koutsopoulou;IEEE Commun. Surveys,2004
4. 3G TR 23.815 version 5.0.0, 3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; Service aspects; Charging implications of IMS architecture (Release 5).
5. 3GPP TS 29.198-1 version 5.4.0, 3rd Generation Partnership Project; Technical Specification Group Core Network; Open Service Access (OSA); Application Programming Interface (API); Part1: Overview (Release 5).