1. Department of Management, Economics and Quantitative Methods, University of Bergamo, via dei Caniana 2, 24127 Bergamo, Italy
2. Department of Applied Mathematics III and High Engineering School, (Manresa Campus), Technical University of Catalonia, Av. de les Bases de Manresa, 71-73 Manresa, Spain
3. AGH University of Science and Technology, Faculty of Management ul. Gramatyka 10, 30-067 Krakow, Poland