1. Department of Mathematics, Lahijan Branch, Islamic Azad University, Lahijan, Iran
2. UISPA–LAETA/INEGI, Faculty of Engineering, University of Porto, Porto, Portugal
3. School of Mathematics and Statistics, Hubei Key Laboratory of Engineering Modeling and Scientific Computing, Huazhong University of Science and Technology, Wuhan, China
4. Department of Electrical Engineering, Institute of Engineering, Porto, Portugal