Interval oscillation criteria for second-order nonlinear differential equations with damping

New oscillation criteria are established for the nonlinear damped different ial equation (ry')' +py' + qf(y) = 0 that are different from most known one s in the sense that they are based on the information only on a sequence of subintervals of [t(0), infinity], rather than on the whole half-line. Our results are sharper than some previous results, and extend and improve the recent interval criteria of Kong and Huang, and can be applied to extreme c ases such as J(t0)(infinity) q(s) ds = -infinity. In particular, several ex amples that dwell upon the sharp conditions of our results are also include d. (C) 2000 Elsevier Science Ltd. All rights reserved.