“…is Hölder continuous in R 4 (because Φ ∈ C α (D)) and therefore the following fourdimensional Fourier series of ω, where ϕ ijkl (x , y , p , q ) = ϕ i (x )ϕ j (y )ϕ k (p )ϕ l (q ), converges uniformly [13]: Similarly, let w i denote the representative of γw φi with zero mean. By Theorem 2.1 and Lemma 3.10, ∂D w p,q φ i ds = w i (p)−w i (q) and λ ij = λ ji = ∂D w i φ j ds for all i, j = 0, 1, 2, .…”