1. Department of Applied Mathematics, University Politehnica of Bucharest, 060042 Bucharest, Romania
2. Academy of Romanian Scientists, 54 Splaiul Independentei, 050094 Bucharest, Romania
3. Fundamental Sciences Applied in Engineering Research Center (SFAI), University Politehnica of Bucharest, 060042 Bucharest, Romania
4. Department of Mathematics, COMSATS University Islamabad, 44000 Islamabad, Pakistan
5. Department of Mathematics, Institute of Technical Education and Research, Siksha O Anusandhan University, Bhubaneswar 751030, Odisha, India
6. Department of Mathematics, Faculty of Science, Khon Kaen University, 40002 Khoon Kaen, Thailand