Ralević, P. ., Dobrodolac, M. ., Švadlenka, L. ., Šarac, D. ., & Đurić, D. . (2020). Efficiency and productivity analysis of universal service obligation: a case of 29 designated operators in the European countries. Technological and Economic Development of Economy, 26(4), 785-807. https://doi.org/10.3846/tede.2020.12062