Frank Windmeijer (1997). An R-squared measure of goodness of fit for some common nonlinear regression models Journal of Econometrics.
                Frank Windmeijer (1997). An R-squared measure of goodness of fit for some common nonlinear regression models Journal of Econometrics.
                
                
                
                Frank Windmeijer (1997). Endogeneity in count data models: An application to demand for health care Journal of Applied Econometrics.