1. Instituto de Economia e Gestao, Technical University of Lisbon, Rua Miguel Lupi 20, 1249-078 Lisbon, Portugal
2. School of Recreation, Health and Tourism, College of Education and Human Development, George Mason University, 10900 University Blvd, Manassas, VA 20110, USA
3. University of Azores, Rua da Mãe de Deus 58, 9501-801 Ponta Delgada, Azores, Portugal