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Astron. Astrophys. 359, 780-787 (2000) AcknowledgementsWe are indebted to G.V. Efimov, Ph. Rosenau, G. Kanschat and G. Shaviv for many helpful discussions. This work has been supported in part by the DFG (Sonderforschungsbereich 359/C2). ![]() ![]() ![]() ![]() © European Southern Observatory (ESO) 2000 Online publication: July 7, 2000 ![]() |