“…For basic properties of k-convolution, see Balser [1,2], Ouchi [8,9] and Tahara-Yamazawa [11]. For simplicity, we use the notations: u * k 2 = u * k u, u * k 3 = u * k u * k u and so on, i=1,2 * k u i = u 1 * k u 2 , i=1,2,3 * k u i = u 1 * k u 2 * k u 3 and so on.…”