As shown in Reference 7, the problem can be solved
via the Newton interpolation scheme, which is known to
become critical if the eigenvalues pi of A are close. The
freedom of choice of the parameters si removes this
trouble. Moreover, the recourse to the Newton scheme
can be avoided, if we choose the parameters s j , j = 1, . . . ,
n, equal to the desired closed-loop eigenvalues. In this
case, we have, immediately: