1. Department of Mathematics, University of Malakand, Chakdara Dir (L), Khyber Pakhtunkhwa 18800, Pakistan
2. Department of Mathematics, Government Degree College Gulabad Dir (L), Khyber Pakhtunkhwa 25000, Pakistan
3. Department of Electricity and Electronics, Institute of Research and Development of Processes, University of the Basque Country, Campus of Leioa, 48940 Leioa, Bizkaia, Spain