“…In [8], Long et al considered the following initial-boundary value problem u tt − u xx + t 0 k(t − s)u xx ds + |u t | q−2 u t = f (x,t, u), (x,t) ∈ (0, 1) × (0, T ), u x (0,t) = u(0,t), u x (1,t) + ηu(1,t) = g(t), u(x, 0) = u 0 (x), u t (x, 0) = u 1 (x), where η ≥ 0, q ≥ 2 are given constants and u 0 , u 1 , g, k, f are given functions. The first result obtained in [8] is the unique existence of a weak solution u(t). On the other hand, in case of f (x,t, u) = −|u| p−2 u + F(x,t), the solution u(t) is exponentially decay to zero as t → +∞.…”