1. Corresponding author. Department of Mathematics and Computer Science, Faculty of Health, Science and Technology, Karlstad University, Karlstad, Sweden.
2. Institute of Mathematics and Scientific Computing, University of Graz, Heinrichstraße 36, 8010 Graz, Austria.
3. Division of Mathematical Science, Department of Systems Innovation, Graduate School of Engineering Science, Osaka University, Machimaneyamacho 1-3, Toyonakashi, 560-8531, Japan.