TY - JOUR A1 - Bove, I. A1 - Boccaletti, Stefano A1 - Bragard, Jean A1 - Kurths, Jürgen A1 - Mancini, H. T1 - Frequency entrainment of nonautonomous chaotic oscillators N2 - We give evidence of frequency entrainment of dominant peaks in the chaotic spectra of two coupled chaotic nonautonomous oscillators. At variance with the autonomous case, the phenomenon is here characterized by the vanishing of a previously positive Lyapunov exponent in the spectrum, which takes place for a broad range of the coupling strength parameter. Such a state is studied also for the case of chaotic oscillators with ill-defined phases due to the absence of a unique center of rotation. Different phase synchronization indicators are used to circumvent this difficulty Y1 - 2004 ER -