Regression Model With Elliptically Contoured Errors
  For the regression model where the errors follow the elliptically contoured distribution (ECD), we consider the least squares (LS), restricted LS (RLS), preliminary test (PT), Stein-type shrinkage (S) and positive-rule shrinkage (PRS) estimators for the regression parameters. We compare the quadratic risks of the estimators to determine the relative dominance properties of the five estimators. 
M. Arashi, A. K. Md E. Saleh, S. M. M. Tabatabaey
math.ST stat.ME stat.TH