1. Instituto Universitário de Lisboa (Iscte), Cis-Iscte, 1649-026 Lisbon, Portugal
2. Instituto de Ciências Sociais, Universidade de Lisboa, 1600-189 Lisbon, Portugal
3. Department of Quantitative and Business Studies, University of Naples, 80132 Napoli, Italy
4. Sociology Department, South-West University “Neofit Rilski”, 2700 Blagoevgrad, Bulgaria