Comments on "On the inverse optimum control problem for a class of nonlinear autonomous systems"

The purpose of this correspondence is to indicate an error in Thau´s paper in the expression for the part of the loss function involving the state variables, and to derive a corrected and simplified version for this expression. Furthermore, a condition in the frequency-domain is presented that is necessary as well as sufficient for the loss function involving the state variables to be nonnegative definite.