Astron. Astrophys. 324, 877-887 (1997)

Acknowledgements

We would like to thank T.S. van Albada for his stimulation to start this project and H. van Woerden for his comments on the manuscript. We also thank the anonymous referee for useful suggestions. This research has made use of the LEDA database which is maintained by the Observatoire de Lyon and Observatoire de Paris-Meudon. We are grateful to the Netherlands Foundation for Research in Astronomy (ASTRON) and the Netherlands Organization for Scientific Research (NWO) for their support. AHB wishes to thank the Swedish Natural Science Research Council (NFR) for their financial support.

© European Southern Observatory (ESO) 1997

Online publication: May 5, 1998

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