1. Transparency Market Research. (2014). VoIP Services Market (Corporate Consumers and Individual Consumers)—Global Industry Analysis, Size, Share, Growth, Trends and Forecast, 2014–2020. Retrieved December 25, 2014 from https://www.reportbuyer.com/product/2362889/ .
2. Cano, M.-D., & Cerdan, F. (2012). Subjective QoE analysis of VoIP applications in a wireless campus environment. Telecommunication Systems, 49(1), 5–15.
3. ITU-T (1994) Recommendation E.800: Terms and definitions related to quality of service and network performance including dependability. http://www.itu.int/ . Accessed 8 Feb 2014.
4. Takahashi, A., Hands, D., & Barriac, V. (2008). Standardization activities in the ITU for a QoE assessment of IPTV. IEEE Communications Magazine, 46(2), 78–84.
5. Alben, L. (1996). Defining the criteria for effective interaction design. Interactions, 3(3), 11–15.