K. M. wishes to acknowledge the financial support received from the Universitat de les Illes Balears. R. O. and J. L. B. want to acknowledge the financial support received from DGICYT under grant PB96-0092. A part of these computations was performed using a Cray YMP/4E at ICM of the University of Warsaw. K. M. expresses his thanks to Rick DeVore for providing the code and for several discussions on numerical issues. The authors thank an unknown referee for some stimulating comments.
© European Southern Observatory (ESO) 1998
Online publication: January 16, 1998