1. Department of Political and Social Sciences, University of Catania, via Vittorio Emanuele II 49, 95131 Catania, Italy; Istituto Nazionale di Geofisica e Vulcanologia, Osservatorio Etneo - sez. di Catania, 95125 Catania, Italy
2. Department of Agriculture, Food and Environment, University of Catania, Via Santa Sofia 98-100, 95123 Catania, Italy
3. Department of Educational Sciences, University of Catania, via Biblioteca 4, 95124 Catania, Italy