1. Mathematical Institute of the Serbian Academy of Sciences, Knez Mihailova 36/Ⅲ, Beograd 11000, Serbia
2. Department of Medical Research, China Medical University Hospital, China Medical University, Taichung 40402, Taiwan
3. Faculty of Electrical Engineering, University of Belgrade, Bulevar Kralja Aleksandra 73, Beograd 11000, Serbia
4. Faculty of Mechanical and Civil Engineering in Kraljevo, University of Kragujevac, Kraljevo, Serbia
5. Deptartment of Mathematical Sciences, Appalachian State University, Boone, NC 28608, USA