1. School of Mathematical Sciences, Universiti Sains Malaysia, 11800 Penang, Malaysia
2. Informetrics Research Group, Ton Duc Thang University, Ho Chi Minh City, Vietnam
3. Faculty of Mathematics and Statistics, Ton Duc Thang University, Ho Chi Minh City, Vietnam
4. Department of Mathematics, University of Sargodha, 40100 Sargodha, Pakistan
5. Department of Mathematics, University of Management and Technology, C-II Johar Town Lahore, Pakistan
6. Institute for Groundwater Studies, Faculty of Natural and Agricultural Sciences, University of the Free State, South Africa