To refer to this article use this url: http://dpc.uba.uva.nl/ctz/vol68/nr01/art02
Acknowledgements
This research has been made possible by a grant (no. 750.195.17) from the ‘Stichting Geologisch, Oceanografisch en Atmosferisch Onderzoek‘, Nederlandse Organisatie voor Wetenschappelijk Onderzoek (the Foundation for Geological, Oceanographic and Atmospheric Research, the Dutch Organization for Scientific Research). Thanks are also extended to an anonymous reviewer and the Dr. G.F. Wilson for their valuable comments.