Participated in the workshop: Frontiers of Combinatorics, at Los Alamos National Laboratory,
New Mexico, USA, from July 29 - August 7, l998.
Under exchange of scientists programme of Indian National Science Academy,
New Delhi and Japan society for promotion of science,
Tokyo to Hiroshima University,
Japan from 3rd-- 23rd September, 1991.
Under International collaboration programme of European commission and ministry of Science and Technology,
Government of India, to Institute of Mathematics and and Statistics,
University of Kent, Canterbury,
U.K. from 17 December 1991 to 16th August 1992.
Under visiting scientists programme, to Indian Statistical Institute,
Calcutta from April, 1 to 30,1997.
Under visiting scientists programme, to Indian Statistical Institute,
New Delhi from September 9 to October 8,1999.
Under visiting scientists programme, to Indian Institute of Technology,Kharagpur, from October 13 to October 17,2003;27-30March,2007.
Under visiting scientists programme, to Korea Advanced institute of Science and Technology, Daejon from March 16 to 23,2004;Dec.2005;Sept.2006.
Under visiting scientists programme, to School of Information Science,University of Nagoya,Nagoya,Japan from September 24 to 28,2006.