Apr.-May.1990 Finnish Academy of Sciences
Lecture tour in the University of Yuvaskyla, Turku, Helsinki

June-July.1995 Japanish Agency of Industrial Research, Tsukuba, Japan

Apr.1997 Environmental Protection Agency of USA (US EPA)
Resarch Triangle Park, North Carolina

Jan.-Feb. 2001 Lecture tour, PSG College of Arts & Science, Coimbatore, Lady Doak College, Madurai, Hindu College, Nagerkoil, Presidency College, Chennai - India