Department of Mathematics, Faculty of Science, Zagazig University, Zagazig, Egypt
Department of Mathematics, Faculty of Science, Zagazig University, Zagazig, Egypt
Department of Mathematics, Faculty of Science, University of Benghazi, Benghazi, Libya
Copyright © 2015 Amr M. S. Mahdy, Adel S. Mohamed, Ahmad A. H. Mtawa et al. This is
an open access article distributed under the Creative Commons Attribution
License, which permits unrestricted use, distribution, and reproduction in any
medium, provided the original work is properly cited.