Li-Ping ZHU, Li-Xing ZHU and Zheng-Hui FENG: Dimension reduction in regressions through cumulative slicing
        estimation, To appear in Journal of the American Statistical Association (2010).
Le-Xin LI, Li-Ping ZHU and Lixing ZHU: Inference on primary parameter of interest with aid of dimension reduction
        estimation, To appear in Journal of the Royal Statistical Society, Series B (2010).