[1] Univ Linz, Inst Finanzmath, A-4040 Linz, Austria
[2] Univ Technol Sydney, Sch Finance & Econ, Sydney, NSW 2007, Australia
[3] Univ New S Wales, Sch Math & Stat, Sydney, NSW 2052, Australia
[4] Katholieke Univ Leuven, Dept Comp Sci, B-3001 Heverlee, Belgium