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Astron. Astrophys. 335, 449-462 (1998) AcknowledgementsWe would like to thank the referee, Nicola Caon, for useful comments. This work was partially supported by the Estonian Science Foundation through grants 180 and 2627. ![]() ![]() ![]() ![]() © European Southern Observatory (ESO) 1998 Online publication: June 18, 1998 ![]() |