[1] Univ Strathclyde, Dept Math & Stat, Glasgow G1 1XH, Lanark, Scotland
[2] Weierstrass Inst Appl Anal & Stochast WIAS, D-10117 Berlin, Germany
[3] Free Univ Berlin, Dept Math & Comp Sci, D-14195 Berlin, Germany
[4] Charles Univ Prague, Fac Math & Phys, Dept Numer Math, Prague 18675 8, Czech Republic