Ismail, I., S. H. Supangkat, H. Hendrawan, and B. Y. Iskandar. “Refining Spectrum Fee to Increase Utilization Efficiency by Adopting ITU-R SM 2012-2 Case Study: Cellular Service in Indonesia”. Journal of ICT Research and Applications, vol. 4, no. 1, Sept. 2013, pp. 1-22, doi:10.5614/itbj.ict.2010.4.1.1.