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Astron. Astrophys. 326, 608-613 (1997)
Acknowledgements
TB is supported by NWO under grant PGS 78-277. GT acknowledge partial support from the Italian Space Agency. This research has made use of the SIMBAD database. We thank S. Randich for useful discussion and comments to the manuscript.
© European Southern Observatory (ESO) 1997
Online publication: October 15, 1997
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