1. Mathematical Institute of the Serbian Academy of Sciences Beograd Serbia
2. Department of Medical Research China Medical University Hospital, China Medical University Taichung 40402 Taiwan Republic of China
3. Department of Computer Science and Information Engineering Asia University Wufeng, Taichung 41354 Taiwan Republic of China
4. Department of Mathematics, Faculty of Electrical Engineering and Communication Brno University of Technology Brno Czech Republic
5. Faculty of Electrical Engineering Belgrade University Beograd Serbia
6. Department of Mathematical Sciences Appalachian State University Boone North Carolina