1. Faculty of Economic Sciences, Valahia University of Targoviste, Targoviste, Romania
2. Faculty of Economics, Hyperion University of Bucharest, Bucharest, Romania
3. Institute of Multidisciplinary Research for Science and Technology of Valahia University of Targoviste, Targoviste, Romania
4. Institute of National Economy, Romanian Academy, Bucharest, Romania; Faculty of Economics, Hyperion University of Bucharest, Bucharest, Romania