“…One way is to consider regularity criteria involving only one velocity component, which were done in [3], [9], [10], [13], [25], [27], and the references therein. Another way is to study the possible components reduction of ∇u to ∇u 3 , see for instance [4], [5], [7], [10], [16], [20], [22], [24], [26], [27]; or to ∂ 3 u, see for example [2], [11], [15], [14], [23]. In [14], Penel and Pokorný showed that if (1.4)…”