With Katalin Balla, Miskolc, Hungary, May, 2003

Oberwolfach, Germany, April 2006

Bedlewo, Poland, April, 2007

With W. Gear, Oberwolfach, Germany, April 2006

With G. Kurina, Oberwolfach, April 2006 

With R. Maerz, Berlin, Germany, April, 2007

With V. Mehrmann and H. Xu, Berlin, March, 2007

With L. Petzold, Santa Barbara, USA, April, 2008

With Prof. Helmut Schwarz, President of Humboldt Foundation, Bonn, April, 2009

Discussion with V. Mehrmann and E. Van Vleck, Berlin, April 2009

Farewell with Volker Mehrmann, Ivan Slapnicar, and Safique Ahmad, Berlin, August, 2009

With Prof. Dinh Nho Hao, Berlin, August, 2009

With Pham Huu Anh Ngoc at the AVH annual meeting, Berlin, June, 2009

With Prof. Duong Minh Duc, Prof. Pham Ky Anh, and Prof. Keonhee Lee, October, 2009

With Prof. Nguyen Khoa Son, Prof. Nguyen Huu Du, and Prof. Keonhee Lee, Halong, October, 2009

C. Mehl, D.S. Mackey, S. Gugercin&his fiancee, M. Gutknecht&his wife, N. Mackey, Volker, and myself (Berlin, April, 2010)
Congratulation to Ngo Bao Chau, one of the 2010's Fields medalists (Hanoi, September, 2010)
With Steve Campbell, Banff, October, 2010
At Emerald Bay, Lake Tahoe, June, 2011