“…We perform the congruent transformation on Θ( θ ): premultiplying an invertible symmetric matrix diag{ P ( θ ) −1 , P ( θ ) −1 , P ( θ ) −1 , S −1 , I } and, meanwhile, postmultiplying the transposition of this matrix, then denoting X ( θ ) = P ( θ ) −1 , , , and , ( l = 1, 2), we have Obviously, the nonlinear terms still exist in . From the work of Wang et al, we have …”