https://www.academia.edu/95025187/On_marginal_estimation_in_a_semiparametric_model_for_longitudinal_data_with_time_independent_covariates
We consider M-estimators for a class of semiparametric mixed-e¤ect models without time-dependent covariates and show that the simple marginal estimation method...
in asemiparametric modelpdfmarginalestimation