1. Department of Industrial Engineering and Management, College of Engineering, Peking University, Beijing 100871, China
2. The Robert H. Smith School of Business, Institute for Systems Research, University of Maryland, College Park, Maryland 20742
3. Department of Management Science, School of Management, Fudan University, Shanghai 200433, China
4. Department of Econometricsand Operations Research, Vrije Universiteit Amsterdam, 1081 HV Amsterdam, Netherlands