1. Occupational Health Service, Healthcare Area IV Public Health Service of the Principality of Asturias (SESPA) Oviedo Spain
2. Doctoral Programme in Health Sciences University of Alicante Alicante Spain
3. Department of Business Administration University of Oviedo Oviedo Spain
4. Department of Mathematics University of Oviedo Oviedo Spain
5. Department of Optics, Pharmacology and Anatomy University of Alicante Alicante Spain
6. Public Health Research Group University of Alicante Alicante Spain