Visiting scientist,  ICTP, Trieste, Italy,  supported by ICTP,  
Jan. to Feb. 1990;

Invited visit,  Graz Univ., Graz, Austria,  supported by Prof. C. B. Lang,  
Mar. 13 to 18, 1990;

Invited talk,  Technical Univ. of Vienna, Vienna, Austria,  
supported by Prof. H. Markum,  
Mar. 18 to 20, 1990;

Visiting scientist and invited talk,  Free Univ., Berlin, Germany,  
supported by DAAD,  invited by Prof. V. Linke, 
Mar. 21 to Apr. 19, 1990;

Invited visits and invited talks,  Waseda Univ. and Tokuyama Univ., Japan,  
supported by Prof. M. Namiki, K. Okano and DFG,  
Apr. to May 1992;

Invited visits and invited talks,
Waseda Univ., Tokyo Metropolitan Univ. and Tokuyama Univ., Japan, 
supported by Prof. M. Namiki, H. Minakata, K. Okano and DFG,  
Apr. to May 1994;

Invited talk,  Essen Univ.,  Essen, Germany,  supported by Dr. U. Ritschel,  
Apr. (two days), 1994;

Invited visit,  Essen Univ., Essen, Germany,  supported by Dr. U. Ritschel,  
Jun. (one week), 1994;

Invited talk,  Mainz Univ., Mainz, Germany,  supported by Dr. B. Duenweg,  
Oct. (two days), 1995;

Invited talk,  Wuppertal Univ., Wuppertal, Germany,  supported by Prof. P. Grassberger,  
Nov. (one day), 1995;

Invited talk,  Halle Univ., Halle/s, Germany,  supported by Prof. S. Trimper, 
Jul. 22 to 28, 1997;

Invited talk,  Siegen Univ., Siegen, Germany,  supported by Prof. L. Schuelke,  
Dec. (one week), 1997;

Invited visits,  Siegen Univ., Siegen, Germany,  
supported by Siegen Univ., invited by Prof. L. Schuelke, 
Jan. 1998 to Apr. 1999, two or three weeks for every two months;

Colloquium,  Free Univ., Berlin, Germany,  
supported by Free Univ., invited by Prof. V. Linke,  
Dec. 17 to 19, 1998;

Invited talk,  Institut fuer Festkoerperforschung, Juelich, Germany,  
supported by Dr. G. M. Schuetz,  
Feb. 3 to 5, 1999;

Invited visit,  Duesseldorf Univ., Duesseldorf, Germany,  supported by Prof. H. K. Janssen,  
Feb. 4 to 5, 1999;

Invited visits,  Free Univ., Berlin, Germany,  supported by Prof. V. Linke,  
Jun. 1999 to 2001.10, some days for every month.

Visiting scientist,  Institute for Theoretical Physics, Beijing, China,  
supported by NNSF,  
Jan. to May 2000;

Visiting scientist,  ICTP, Trieste, Italy,  supported by ICTP and L. Yu,  
Jan. 13 to Apr. 17, 2001;

Invited visit,  Halle Univ., Halle/s, Germany,  supported by Prof. S. Trimper, 
Dec, 2002 to Jan. 2003;

Invited visit,  Halle Univ., Halle/s, Germany,  supported by Prof. S. Trimper, 
Dec, 2004 to Jan. 2005;

Invited talk,  Kassel Univ., Kassel, Germany,  supported by Prof. D. Kolb, 
Jan. 24-26, 2005;

Invited talk,  Leipzig Univ., Leipzig, Germany,  supported by Prof. W. Janke, 
Feb. 3, 2005;

Invited talk, Center of Theo. Sci., Xinzhu, Taiwan, supported by Prof. CH Chang,
May 13, 2005;

Invited talk, Central Univ., Zhongli, Taiwan, supported by Prof. HC Lee,
May 16-18, 2005;

Invited talk, Zhongxinh Univ, Taizhong, Taiwan, supported by Prof. SS Liaw,
May 19-20, 2005;

Invited visit, ICTP, Trieste, Italy, supported by ICTP,
July 11 - Sep. 16, 2005;

Invited visit and talk, Halle Univ., Halle, Germany supported by Prof. S Trimper,
Aug. 8-12, 2005;

Invited visit, NIMS, Tsukuba, Japan, supported by Prof. X Hu,
Jan. 20 Feb. 19, 2006;

Invited talk, Tokuyama Univ., Tokuyama, Japan, supported by Prof. K Okano,
Feb. 9-12, 2006;

Invited talk, Tokyo Metropolitan Univ., Tokyo, Japan, supported by Prof. Y Okabe,
Feb. 13, 2006;

Invited talk, Waseda Univ., Tokyo, Japan, supported by Prof. H. Nakazato,
Feb. 17, 2006;

Invited visit, Nat. Univ. Singapore, Singapore, supported by Prof. JS Wang,
Feb. 19 - 26, 2006;