1. Department of Mathematics, COMSATS University Islamabad, Sahiwal, Pakistan
2. Facultad de Ciencias Naturales y Exactas, Escuela de Ciencias FÃ-sicas y MatemÃ! ticas, Pontificia Universidad CatÃlica del Ecuador, Sede Quito, Ecuador
3. Institute of Mathematical Sciences, Universiti Malaya, Kualal Lumpur Malaysia
4. Research department, QFBA-Northumbria University, Doha, Qatar
5. Department of Mathematics, Government College University Faisalabad Sahiwal Campus, Pakistan
6. Department of Mathematics, Düzce University, Düzce, Turkey