1. Department of Surgery, Faculty of Medicine, University of Salamanca. Salamanca, Spain
2. Department of Stomatology, Faculty of Odontology, University of Seville, Seville, Spain
3. Department of Sociology, Social Work and Public Health, Faculty of Labour Sciences, University of Huelva, Huelva, Spain
4. Safety and Health Postgraduate Programme, Universidad Espíritu Santo, Guayaquil, Ecuador.