“…The stabilization of reaction-diffusion PDEs with an arbitrary level of instability and under arbitrarily long input delay is a challenging problem, first formulated and solved in [27] using the backstepping method for PDEs as the stabilization of a hyperbolic (transport) PDE which cascades into the reaction-diffusion PDE. Since then, control design for delay compensation (including known or unknown constant/timevarying delays) has evolved considerably and several results have been proposed for reaction-diffusion PDEs, see, e.g., [12,14,32,23,35,4,44] and the references therein.…”