Author comment for 2004PhDT..........V:
The full text of this article is electronically available from the author's
home institution the URL:
https://www.astro.uu.nl/~jleeuwen/phd_thesis
Author comment submitted on 23 June, 2004 by Joeri vn Leeuwen (a.g.j.vanleeuwen@astro.uu.nl)