| ? | Visiting Professor at the University of Oslo, Norway, Oslo, November, 2010 |
| ? | Visiting Professor at the Hamilton Institute of Mathematics, Dublin, Ireland, September 2010 |
| ? | Visiting Professor at the University of Ljubljana, Slovenia, August, June 2010 |
| ? | Visiting Professor at INRIA, Saclay, and Ecole Polytechnique, CMAP, France, Paris, April 2010 |
| ? | Visiting Professor at the University of Tras-os-Montes and Alto Douro, Vila Real, Portugal, March 2010 |
| ? | Visiting Professor at the University of Patras and the University of Athens, Greece, June-July 2009 |
| ? | Visiting Professor at the Institute of Mathematics, Physics and Mechanics, Slovenia, Ljubljana, August 2008, June 2009 |
| ? | Visiting Professor at INRIA, Saclay, and Ecole Polytechnique, CMAP, France, Paris, April, June ? August and November 2008 |
| ? | Visiting Professor at the University of Stockholm, Sweden, January ? June, 2007 |
| ? | Visiting Professor at INRIA, Rocquencourt, France, Paris, June ? August 2006 |
| ? | London Mathematical Society Lectureship Fellow at the University of Birmingham, UK, Birmingham, October 2005 |
| ? | Visiting Professor at the University of Dortmund, Germany, Dortmund, June ? August 2005 |
| ? | Visiting Professor at the University of Dortmund, Germany, Dortmund, September ? December 2004 |
| ? | Visiting Professor at the Bielefeld University, Germany, Bielefeld, July 2004 |
| ? | Visiting Professor at the Porto University, Portugal, Porto, September 2003 |
| ? | Visiting professor at Sung Kyun Kwan University and Pohang Institute of Science and Technology, Korea, Seoul, Pohang, January 2003 |
| ? | Visitor in the Weizmann Institute of Science, Israel, Rehovot, May ? August 1997 |