| Institution: | 1. Department of Mathematics, Faculty of Education, Alexandria University, Egypt;2. Department of Mathematical and Physical Sciences, Nizwa University, Nizwa 611, P.O. Box 1357, Oman;3. Arab Academy for Science and Technology, P.O. Box 1029 Alexandria, Egypt;1. Department of Mathematics, Faculty of Education, Alexandria University, Alexandria, Egypt;2. Arab Academy for Science and Technology, P.O. Box 1029, Alexandria, Egypt;1. Eberhard Karls Universität Tübingen, Germany;2. Ghent University, Belgium |
