| From | To | Position | Institution |
|---|---|---|---|
| 2002 | Jul-Aug | Visiting Professor | Erwin Schroedinger International Institute for Mathematical Physics(Austria) |
| 1999 | July | Visiting Professor | Instituto Argentina de Matematica(Argentina) |
| 1999 | March | Visiting Professor | Institut des Hautes Etudes Scientifiques(France) |
| 1994 | Present | Adjunct Professor | University of Illinois at Urbana-Champaign (USA) |
| 1988 | Present | Professor | Eastern Illinois University (USA) |
| 1992 | 1994 | Visiting Scientist (DMS Program Directorship in Geometric Analysis) | The National Science Foundation (USA) |
| 1991 | May-Jul | Visiting Professor | University of Aarhus (Denmark) |
| 1988 | May-Aug | Visiting Professor | The Institute for Advanced Study (USA) |
| 1986 | 1988 | Visiting Professor | Rutgers University (USA) |
| 1985 | 1986 | Postdoctoral Fellowship | McMaster University (Canada) |
| 1984 | 1985 | Solomon Lefschetz Visiting Professor | CINVESTAV-IPN (Mexico) |