[1] Northwest Univ, Dept Math, Kano, Nigeria
[2] Univ Dschang, IUT FV Bandjoun, Lab Automatiqueetd Informat Appl LAIA, BP 134, Bandjoun, Cameroon
[3] Amol Univ Special Modern Technol, Fac Engn Technol, Amol, Iran
[4] Univ Punjab, Dept Math, Lahore 54590, Pakistan
[5] Imarli St 28-4, TR-26030 Eskisehir, Turkey