Institution: | College of General Education, Osaka Sangyo University, Nakagaito 3-1-1, Daito, Osaka 574-8530, Japan ; Graduate School of Humanities and Sciences, Nara Women's University, Kitauoyanishi-machi, Nara 630-8506, Japan ; Department of Mathematics and Mathematics Education, Hiroshima University, Kagamiyama 1-1-1, Higashi-hiroshima, Japan 739-8524. |