“…In this work, the authors used the energy method and the spectral analysis for the optimal decay estimates on the linearized problem to establish the existence, but unfortunately, even using the optimal decay estimates, the existence can be proved only when the space dimension N ≥ 5. In a recent work [1,2], Bȓezina and Kagei considered the time-periodic parallel flow in a N-dimensional infinite layer R N −1 × (0, l), in the papers, by using the solution of a one-dimensional heat-type equation in a bounded domain (0, l), and the authors constructed a periodic solution for the Navier-Stokes equations with a special time-periodic external force of this form f = (f 1 (x n , t), 0, . .…”