“…Furthermore, for the closely related analysis of hypo-and multi-quasi-elliptic operators we refer to [1,3,4,6,22,25,42,41]. Even though the focus of this work lies on classical Sobolev-and hence L 2 -based results, note that a great number of L p -boundedness results for (different classes of) anisotropic integral operators can be found in [10,16,29,40,46] and the references there.…”