1. Department of Mathematics, Ramanujan School of Mathematical Sciences, Pondicherry University, Puducherry 605014, India
2. Institute of Applied Mathematics, John von Neumann Faculty of Informatics, Óbuda University, Bécsi út 96/b, 1034 Budapest, Hungary
3. Faculty of Maritime Studies, University of Rijeka, Studentska 2, 51000 Rijeka, Croatia