1. Business Administration Department, Petroleum-Gas University of Ploiesti, Ploiesti, Romania
2. National Institute of Economic Research, “Costin C. Kiriţescu”, Romanian Academy, Bucharest, Romania
3. Doctoral School Economics II, The Bucharest University of Economic Studies, Bucharest, Romania
4. Faculty of Economic Sciences, Valahia University of Târgoviște, Târgoviște, Romania