[1] Natl Univ Singapore, Dept Math, Block S17 Level 4,2 Sci Dr 2, Singapore 117543, Singapore
[2] Natl Univ Singapore, Risk Management Inst, 21 Heng Mui Keng Terrace,04-03, Singapore 119613, Singapore
[3] Tech Univ Berlin, Dept Math, Str 17 Juni 136, D-10623 Berlin, Germany
[4] Zuse Inst Berlin, Math Optimizat Dept, Takustr 7, D-14195 Berlin, Germany
[5] Natl Univ Singapore, Fac Sci, Dept Stat & Appl Probabil, Block S16 Level 4,6 Sci Dr 2, Singapore 117546, Singapore
[6] Nanjing Univ Informat Sci & Technol, Business Sch, Nanjing 210044, Peoples R China
[7] Jinan Univ, Dept Management, Guangzhou 510632, Guangdong, Peoples R China