1. Department of Mathematics, University of Oslo, PO Box 1053 Blindern, Oslo N-0316, Norway
2. Department of Mathematical Sciences, Aalborg University, Skjernvej 4A, Aalborg Øst 9220, Denmark
3. Quantitative Analytics, Centrica Energy Trading, Skelagervej 1, Aalborg 9000, Denmark
4. Department of Mathematics, Aarhus University, Ny Munkegade 118, Aarhus C 8000, Denmark