Abdel-Rahiem Ibrahim Sadek received the B.Sc. degree in Mathematics in 1983, the M.Sc. degree in Mathematics in 1988, the Ph.D. degree in Mathematics in 1991, and the Associate Professor in 2000, from Assiut University, Egypt. He is an Professor from 2006 till now at Department of Mathematics at Faculty of Science, Assiut University, Egypt. His research interests include stability, boundedness and periodicity of solutions of ordinary and delay differential equations.