Comments on "On limit cycles and the describing function method in periodically switched circuits"

For the original article see IEEE Trans. Circuits Syst., vol. 40, no. 9, p.564-72 (1993). In the aforementioned paper by Sanders it is claimed that a justification for the describing function method is given. Here the commenter observes that this claim is unwarranted, and shows also that earlier results in the literature answer some closely related questions concerning the type of problem addressed in the author's paper.