1. Department of Mathematics, “1 Decembrie 1918” University of Alba Iulia, 510009 Alba Iulia, Romania
2. Department of Applied Mathematics and Science, College of Engineering, National University of Science & Technology, Muscat P.O. Box 620, Oman
3. Department of Mathematics, School of Advanced Sciences, Vellore Institute of Technology, Vellore 632014, Tamilnadu, India