Yohji Akama (1), Atina Husnaqilati (2) (1) Department of Mathematics, Graduate School of Science, Tohoku University, Aramaki, Aoba, Sendai, 980-8578, Japan, Japan,
(2) Department of Mathematics, Graduate School of Science, Tohoku University, Aramaki, Aoba, Sendai, 980-8578, Japan, Japan