1. Department of Mathematics, Faculty of Arts and Science, Namik Kemal University, 59030 Tekirdağ, Turkey
2. Department of Mathematics Engineering, Istanbul Technical University, Maslak, 34469 Istanbul, Turkey
3. Department of Applied Mathematics, Pukyong National University, Busan 608-737, Republic of Korea
4. Department of Mathematics, Faculty of Science and Arts, University of Gaziantep, 27310 Gaziantep, Turkey