“…Results in the same spirit, with an nth-order (n ≥ 3) differential equation in place of (0.1), have been obtained in [4] for linear cases and in [1,2,9] for nonlinear cases. The principal result of the present paper is Theorem 3.1, which generalizes the theorems in [5][6][7]. One can also derive as applications of this theorem various results which, in some cases, improve the theorems in [1,2,4,9].…”