I thank Dr. L. O. Lodén for providing most of the observational data concerning OCRs and for his useful comments and Dr. J.-C. Mermilliod for his valuable remarks on open cluster data. I would like to thank Dr. S. J. Aarseth for a critical reading of this paper. This research has been made use of SIMBAD (operated at CDS, Strasbourg, France), BDA (operated at the Institute of Astronomy, University of Lausanne, Switzerland) and ADS (operated by NASA) databases. The author wishes to thank two anonymous referees for their helpful and insightful comments on the paper.
© European Southern Observatory (ESO) 1998
Online publication: April 20, 1998