“…These systems are infinite dimensional in a sense that the corresponding state variables belong to the infinite-dimensional linear spaces such as the Lebesgue or more generally the Sobolev spaces. One has developed, for example, functional analytic (see, e.g., [1,4,7,16,26]) and algebraic (e.g., [9,20,23]) methods to study these systems. Two of the main issues are the controllability and (asymptotic) output tracking of the system.…”