Mixing for smooth time-changes of general nilflows

We consider completely irrational nilflows on any nilmanifold of step at least 2. show that there exists a dense set smooth time-changes such time-change in this class which is not measurably trivial gives rise to mixing nilflow. This particular reproves and generalizes nilflow (of 2) the main result proved [3] for special Heisenberg (step nilflows, later generalized [58] arbitrary are isomorphic suspensions higher-dimensional linear toral skew-shifts.