1. Department of Mathematical Sciences, Faculty of Science and Engineering, Doshisha University, Kyotanabe City, Kyoto, Japan
2. Graduate School of Informatics, Kyoto University, Kyoto, Japan
3. Centre de recherches mathématiques, Université de Montréal, Montréal (Québec), Canada
4. Institut de valorisation des données (IVADO), Montrèal (Québec), Canada