1. “Babeş-Bolyai” University , Faculty of Economics and Business Administration, Department of Statistics-Forecast-Mathematics , Teodor Mihali Street, No. 58-60, 400591 Cluj-Napoca , Romania
2. “Babeş-Bolyai” University , Faculty of Mathematics and Computer Science, Department of Mathematics , Mihail Kogalniceanu Street, No. 1, 400084 Cluj-Napoca , Romania