1、Nonparametric Analysis of Randomized Experiments with Missing Covariate and Outcome Data
Joel L. Horowitz and Charles F. Manski
Journal of the American Statistical Association
Vol. 95, No. 449 (Mar., 2000), pp. 77-84
(article consists of 8 pages)
Published by: American Statistical Association
Stable URL: http://www.jstor.org/stable/2669526

2、Nonparametric and Semiparametric Models for Missing Covariates in Parametric Regression
Journal of the American Statistical Association

Hua Yun Chen. Journal of the American Statistical Association. December 1, 2004, 99(468): 1176-1189. doi:10.1198/016214504000001727.