• General Linear Model (GLM). In more recent versions of SPSS, MANOVA and MANCOVA are found under "GLM" (General Linear Model). Output is still similar, but with GLM, parameters (coefficients) are created for every category of every factor and this "full parameterization" approach handles the problem of empty cells better than traditional MANOVA. GLM accepts categorical variables which, in SPSS regression, must be manipulated manually as dummy variables. That is, GLM automatically transforms declared categorical variables into sets of indicator variables. GLM calculates parameters using IWLS (iterative weighted least squares). The seminal article on GLM is Nelder and Wedderburn (1972) and an overview is Gill (2001).