In simultaneous equation models (SEMs) the assumption that the covariance matrix of the disturbances is non-singular cannot always be made. For example, allocation models and models with precise observations which may imply linear constraints on the parameters, have singular disturbance...

The General Linear Model (GLM) is the parent model of econometrics. Simultaneous equations and seemingly unrelated regression equation (SURE) models, to name but a few, can be formulated as a GLM. The estimation of the GLM can be viewed as a Generalized Linear Least-Squares problem (GLLSP). The...