1 . paper : Estimating Equations, Empirical Likelihood and Constraints on Parameters
     author : Jing Qin and Jerry Lawless

The Canadian Journal of Statistics / La Revue Canadienne de Statistique
Vol. 23, No. 2 (Jun., 1995), pp. 145-159
(article consists of 15 pages)
Published by: Statistical Society of Canada
Stable URL: http://www.jstor.org/stable/3315441

2 . paper : Testing heteroscedasticity in partially linear models with missing covariates
     author : Xiaohui Liu, Zhizhong Wang & Xuemei Hu

Journal of Nonparametric Statistics Volume 23, Issue 2, 2011