1. Department of Mathematics and Computer Science, Faculty of Science, Menoufia University, Shibin Al Kawm, Egypt
2. Gofa Camp, Near Gofa Industrial College and German Adebabay, Nifas Silk-Lafto, Addis Ababa 26649, Ethiopia
3. Institute of Mathematical Sciences, Faculty of Science, University of Malaya, Kuala Lumpur 50603, Malaysia