Cheng, Gang; Zervopoulos, Panagiotis and Qian, Zhenhua (2011): A variant of radial measure capable of dealing with negative inputs and outputs in data envelopment analysis. Unpublished.
Cheng, Gang and Qian, Zhenhua (2011): DEA数据标准化方法及其在方向距离函数模型中的应用. Forthcoming in: Systems Engineering
Cheng, Gang; Qian, Zhenhua and Zervopoulos, Panagiotis (2011): Overcoming the infeasibility of super-efficiency DEA model: a model with generalized orientation. Unpublished.
