Affiliation: | 1. Emeritus Professor of University of Gunma, 798-8, Hoshikuki, Chuou, Chiba 260-0808, Japan;2. Department of Mathematics, Kinki University, Higashi-Osaka, Japan;3. Department of Mathematics and Computer Science, ?stanbul Kültür University, ?stanbul, Turkey;4. Department of Mathematics and Computer Science, ?stanbul Yeni Yuzyil University, Topkapi ?stanbul, Turkey |