1. Department of Mathematics , Faculty of Science , University of Zakho , 42002 Zakho , Iraq ; and Department of Mathematics, Faculty of Science, Firat University, 23119 Elazig, Turkey
2. Department of Physics , Urmia Branch , Islamic Azad University , 63896 Urmia , Iran
3. Department of Mathematics , Faculty of Science , Firat University , 23119 Elazig , Turkey
4. Computer Science Department , Soran University , 44004 Soran , Iraq