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- Functional – Differential Systems and Related Topics ,
Institute of Mathematics , Polish Academy of Sciences , 1979 , Poland
- Summer Mathematical School , U.N.E.S.C.O. , 1980 , Greece
- On Singularities in Boundary Value Problems , N.A.T.O. , Advanced Study Institute , Maratea , 1980 , Italy
- Symposium on Numerical Analysis and Computational Complex Analysis, E.T.H. , 1983 , Switzerland
- American Mathematical Society Meeting , 1987 , USA
- 94th Annual Meeting of the American Mathematical Society , 1988 , USA
- Technical Institute , Mathematics Department , Zielona Gora , 1990 , Poland
- University of Sofia , Mathematics Department , 1991 , Bulgaria
 AMS Meeting, San Francisco, California, April 29-30, 2006, USA.
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