On the Frequency Theorem for nonperiodic systems

with Roberta Fabbri and Russell Johnson,

in: Dynamics, Bifurcations and Control, 233-241,

Lecture Notes in Control and Information Sciences

ed: Fritz Colonius, Springer-Verlag, 2002.

Using methods of the theory of nonautonomous linear differential systems,

namely exponential dichotomies and rotation numbers, some aspects of

Yakubovich's Frequency Theorem from periodic control systems are

generalized to systems with bounded measurable coefficients.