Department of Mathematical and Systems Engineering;
Faculty of Engineering;
Shizuoka University;
3-5-1 Johoku;
Naka-ku;
Hamarnatsu 432-8551;
Japan;
Department of Mathematics;
Tokyo Institute of Technology;
2-12-1 Oh-okayama;
Meguro-ku;
Tokyo 15248551;
Japan;
Department of Mathematics;
Faculty of Science;
Kyoto Sangyo University;
Motoyama;
Kamigamo;
Kita-ku;
Kyoto 603-8555;
Japan;