“…As pointed out in [11], the above theorem does not require for the coefficient a(t) to be n − 2 times differentiable, which is an advantage over the controllability criterion of [3], [21], [19], [20]. However, the opposite is also true: the systems with n − 2 times differentiable coefficient a(t), that do not satisfy condition (2), can be considered by the criterion of [3], [21], [19], [20].…”