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Astron. Astrophys. 324, 395-409 (1997) AcknowledgementsWe thank the anonymous referee for helpful comments. H. Mause acknowledges financial support by the DARA (50 OR 9301 1). ![]() ![]() ![]() ![]() © European Southern Observatory (ESO) 1997 Online publication: May 26, 1998 ![]() |