“…According to Theorem 3.1, it is possible to draw n stable Routh rays R i (a * ) through an arbitrary stable point a * . In [16] it was shown that if the point is not placed on the boundary of stability domain, then there are positive and negative directions with respect to a * . The positive part of a Routh ray corresponds to α i ∈ (1, ∞) while the negative to α i ∈ (0, 1), and for α i = 1 rays intersect at the point a * .…”