Further comments on "Implications of the Routh stability criterion"

The result of the above-named note (ibid., vol. AC-15 pp 554-555, June 1980) is contained in Routh's original monograph (1975), where he shows that a polynomial has at least one root with a positive real part if any element in the Routh array is negative. Routh's work is readily available in the reprinted version, but for some reason this result is seldom quoted in contemporary textbooks.