[1] Petr Gas Univ Ploiesti, Dept Cybernet Econ Informat Finance & Accounting, Ploiesti, Romania
[2] Inst Natl Econ, Dept Econ, Bucharest, Romania
[3] Vistula Univ, Dept Econ, Warsaw, Poland
[4] Bucharest Univ Econ Studies, Fac Cibernet Stat & Econ Informat, Dept Stat & Econometr, Bucharest, Romania
[5] Inst Natl Econ, Bucharest, Romania
[6] Bucharest Univ Econ Studies, Dept Stat & Econometr, Bucharest, Romania