1. Department of Mathematics, Faculty of Science, Firat University, 23119 Elazig, Turkey
2. Department of Medical Research, China Medical University, Taichung 40402, Taiwan
3. Department of Mathematics and Statistics, College of Science, Imam Mohammad Ibn, Saud Islamic University (IMSIU), Riyadh 11432, Saudi Arabia
4. Department of Mathematics, Texas A & M University-Kingsville, 700 University Blvd., Kingsville, TX 78363-8202, USA