1. a Center of Mathematics for Applications (CMA), University of Oslo , Box 1053 Blindern, N-0316, Oslo , Norway
2. b Norwegian School of Economics and Business Administration (NHH) , Helleveien 30, N-5045, Bergen , Norway
3. c Mathematical Institute, University of Oxford , 24-29 St Giles', Oxford , OX1 3LB , UK
4. d Department of Systems Engineering and Engineering Management , The Chinese University of Hong Kong , Shatin , Hong Kong