“…Although the strategy that we obtain the normal form (which is expressed in the action-angle variables in the tangent directions and Cartesian coordinates in normal directions) in this paper is similar to the one in Ref. 12, the details are quite different (see Subsections II C and II D); (iii) Since the perturbation term (1.4) is related to the time variable t and the spatial variable x, we have to show that the vector field in (2.20) is analytic from l a, s to l a, s when h(θ , x) is analytic in (θ, x) ∈ T m × T d (see Lemma 2.8); (iv) We assume that the forced frequencies are some special forms in Eq. (1.2) and depend on one real parameter ξ ∈ [0, 1] (see (H1)), such that they are non-degenerate, then by using the idea of the measure estimates applied in the paper 13 by Bambusi and Berti, where a degenerate KAM theory for lower dimensional elliptic tori of infinite dimensional Hamiltonian systems depending on one parameter only is studied, we construct a KAM theorem for a dissipative system with a quasi-periodic time-dependent perturbation and one real parameter ξ , and obtain a Cantorian branch of m + 2-dimensional invariant tori for the equation.…”