Contact¶ Shimpei Kobayashi Professor, Department of Mathematics, Hokkaido University Email: shimpei [at] math.sci.hokudai.ac.jp Department of Mathematics, Hokkaido University Nishi 8-Chome, Kita 10-Jou, Kita-Ku Sapporo 060-0810, Japan Links¶ Google Scholar ResearchGate Researchmap KAKENHI