“…Their theorems only concern the situation when (0.1) is linear and (s, m, r, p) = (1, 1, n, n). 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].…”