1. Department of Economics, University of Messina, 98121 Messina, Italy
2. Department of Business Management, Institute of Management, University of Szczecin, 71-004 Szczecin, Poland
3. Department of Econometrics and Statistics, Institute of Economics and Finance, University of Szczecin, Mickiewicza 64, 71-101 Szczecin, Poland
4. Department of Economics, Engineering, Society and Business Organization, University of “Tuscia” of Viterbo, 01100 Viterbo, Italy