On the Moments of Ordinary Least Squares and Instrumental Variables Estimators in a General Structural Equation
G. H. Hillier, T. W. Kinal, V. K. Srivastava, On the Moments of Ordinary Least Squares and Instrumental Variables Estimators in a General Structural Equation, Econometrica, Vol. 52, No. 1 (Jan., 1984), pp. 185-202