The general Gauss-Markov model with possibly singular dispersion matrix

Linear models with possibly singular dispersion (variance-covariance) matrix of the vector of disturbances have been considered in the literature since the late sixties. In this paper we give a survey of important results and consequences without a claim to completeness. Proofs are given for the results in Sections 2 to 5.

1	Notation
2	The General Gauss-Markov Model
3	Best Linear Unbiased Estimation
4	Quadratic Unbiased Estimation
5	Testing a Linear Hypothesis
6	Further Aspects of Linear Estimation