Parametric and Nonparametric Regression with Missing X's - A Review

This paper gives a detailed overview of the problem of missing data
in parametric and nonparametric regression. Theoretical basics,
properties as well as simulation results may help the reader to get
familiar with the common problem of incomplete data sets. Of
course, not all occurences can be discussed so this paper could be
seen as an introduction to missing data within regression analysis
and as an extension to the early paper of Little (1992).