- 2006/04 - 現在 Tohoku University, Divison of Science Mathematical Institute Professor emeritus
- 2006/04 - 2019/03 Tohoku University, Divison of Science Mathematical Institute Visiting professor
- 1989/04 - 2006/03 Tohoku University, Divison of Science Professor
- 2004/09 - 2004/10 Technical University of Munich Department of Mathematics Guest Professor (Humboldt Foundation)
- 1998/07 - 1998/07 University of Lyon Department of Masthematics Guest Professor (Ministry of Education, Culture, Sports, Science and Technology of Japan)
- 1989/07 - 1989/09 サンパウロ大学(USP) (ブラジルFAPESP,FINEP招聘) 数学科 客員教授
- 1974/04 - 1989/03 Tohoku University, College of General Education Associate professor
- 1988/04 - 1988/05 ウオーリック大学(英国) 数学科 客員教授(日本学術振興会派遣研究員)
- 1986/07 - 1986/09 セアラ連邦大学(ブラジル) 理学部数学科 客員教授(ブラジル文部省招聘)
- 1983/07 - 1983/09 セアラ連邦大学(ブラジル) 理学部数学科 客員教授(ブラジル文部省招聘)
- 1978/04 - 1979/03 Humboldt Foundation Department of Mathematics Guest Professor (Humboldt Foundation)
- 1972/04 - 1974/03 Tohoku University, College of General Education Lecturer
- 1968/04 - 1972/03 Tohoku University, Faculty of Science Research assistant
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