1. Trium Analysis Online GmbH, Hohenlindener Str. 1, 81677 München, Germany
2. Department of Mathematical Sciences, Chalmers University of Technology and University of Gothenburg, Chalmers Tvärgata 3, 41296 Göteborg, Sweden
3. Delft Institute of Applied Mathematics (DIAM), Delft University of Technology, Mekelweg 4, 2628CD Delft, The Netherlands