1. Department of Statistics, Computer Science and Mathematics, Public University of Navarre (UPNA), Arrosadia Campus , Pamplona , Spain
2. Institute for Advanced Materials and Mathematics (INAMAT2), Public University of Navarre (UPNA), Arrosadia Campus , Pamplona , Spain
3. Department of Mathematical Sciences, Norwegian University of Science and Technology (NTNU) , Trondheim , Norway