“…Concerning classes of third-order nonlinear evolution equations, there are several works devoted to classify them as nonlinearly self-adjoint and to construct conservation laws via Ibragimov's theorem [10,11,18,19,20,21,41,42]. The relations between Ibragimov's approach and the direct method are well known [4,46,47], and the latter is also largely employed to build up conservation laws for nonlinearly self-adjoint equations [7,13,15,22,30,44].…”