The problem of controlling the output of a system so as to achieve asymptotic tracking of prescribed trajectories and/or asymptotic re jection of undesired disturbances is a central problem in control the ory. A classical setup in which the problem was posed and success fully addressed - in the context of linear, time-invariant and finite dimensional systems - is the one in which the exogenous inputs, namely commands and disturbances, may range over the set of all possible trajectories ofa given autonomous linear system, commonly known as the exogeneous system or, more the exosystem. The case...