1. Department of Mathematics University of Extremadura (Centro Universitario de Plasencia) Plasencia Spain
2. University Institute of Multidisciplinary Mathematics Polytechnic University of Valencia Valencia Spain
3. Vaccine Research Unit Foundation for the Promotion of Health and Biomedical Research of Valencia Region, FISABIO‐Public Health Valencia Spain
4. Department of Community Nursing, Preventive Medicine and Public Health and History of Science University of Alicante San Vicente del Raspeig Spain