1. University School Hunting Valley OH 44022 USA
2. Geomathematics Key Laboratory of Sichuan, Department of Information and Computing Science Chengdu University of Technology Chengdu 610059 China
3. Department of Mathematics SAPIENZA Università di Roma P.le A. Moro, 2 Roma I‐00185 Italy
4. Department of Mathematical Sciences Kent State University Kent OH 44242 USA