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

New oscillation criteria are established for the nonlinear damped differential equation (ry')' +py' + qf(y) = 0 that are different from most known ones 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 cases such as J(t0)(infinity) q(s) ds = -infinity. In particular, several examples that dwell upon the sharp conditions of our results are also included. (C) 2000 Elsevier Science Ltd. All rights reserved.