M. K. Aouf
Mathematics Department, Faculty of Science, Mansoura University, Mansoura 33516, Egypt
R. M. El-Ashwah
Mathematics Department, Faculty of Science, Mansoura University, Mansoura 33516, Egypt
E. E. Ali
Mathematics Department, Faculty of Science, Mansoura University, Mansoura 33516, Egypt; Mathematics Department, Faculty of Science, University of Hail, Kingdome of Saudi Arabia