“…The previous strategy plus some extra (technical) interconnection conditions guarantee that the origin (x, z) = (0, 0) ∈ R ns × R n f is an asymptotically stable equilibrium point of the closed-loop system ( 6) for ε > 0 but sufficiently small [14,24,25,33]. This feature of normal hyperbolicity has been exploited in many applications, a few examples are [10,34,38,43,51,52,54,55].…”