1. Department of Mathematics and Mechanics, China University of Mining and Technology, Xuzhou, Jiangsu 221008, China
2. Department of Chemical and Materials Engineering, Faculty of Engineering, King Abdulaziz University, P.O. Box 80204, Jeddah 21589, Saudi Arabia
3. Department of Mathematics and Computer Sciences, Faculty of Arts and Sciences, Cankaya University, 06530 Ankara, Turkey
4. Institute of Space Sciences, Magurele, 077125 Bucharest, Romania
5. Department of Mathematics and Statistics, University of Victoria, Victoria, BC, Canada V8W 3R4
6. Department of Electrical Engineering, Institute of Engineering of Porto, Rua Dr. António Bernardino de Almeida 431, 4200-072 Porto, Portugal