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Astron. Astrophys. 363, 323-334 (2000) AcknowledgementsThis work was partially supported by the Polish Committee of Scientific Research (K.B.N. grant number 2 P03D 002 09). ![]() ![]() ![]() ![]() © European Southern Observatory (ESO) 2000 Online publication: December 5, 2000 ![]() |