“…The understanding of the nature of ISpS will be beneficial for the development of quantized and sample-data controllers for infinite-dimensional systems and will give further insights into the ISS theory of infinite-dimensional systems in References 14-21. Lyapunov-like characterizations for ISS of finite-dimensional systems described by ordinary differential equations (ODEs) were provided in References 11,12,22. The theory, especially the stability theory, for infinite-dimensional systems has been widely investigated due to the theory development of partial differential equations (PDEs), see References 14,15,18,20,23. In this article, we consider the ISpS for nonautonomous nonlinear infinite-dimensional systems and then obtain some novel criteria by using Lyapunov functions techniques and a nonlinear inequality. The contributions of this paper can be summed as follows.…”