Visiting:

• 2006            Karlsruhe University, Germany     

• 2006            Taiwan University

• 2003-2004  Kansas University, USA

• 2000            Essen University, Germany

• 1998-1999  Karlsruhe University, Germany

• 1993            Köln University, Germany

• 1990-1991  Sheffield University, United Kingdom

     Visitors:

• 2004       T. Puthenpurakal(IIT,Bombay, India)

• 2004       F. Herrlich (Karlsruhe University, Germany)

• 2002       J. Herzog (Essen University, Germany)

• 2001       N.T. Cuong (Mathematics Institute, Vietnam)

• 2001       J. Herzog (Essen University, Germany)

• 2000       F. Herrlich (Karlsruhe University, Germany)

• 1997       F. Herrlich (Karlsruhe University, Germany)

     Talks:

• 2006    Karlsruhe University, Germany

• 2006    Taiwan University, Soochow University, Taipei

• 2006    Institute of Mathematics, Hanoi

• 2004    ICTP, Trieste; Missouri University; Washington State
               University; Idaho University

• 2003    Kansas University; Kansas State University

• 2002    ICM Algebra Satellite Conference

• 2000    Essen University; Karlsruhe University

• 1998    Karlsruhe University

• 1996    Institute of Mathematics, Hanoi