New Kamenev-type oscillation criteria for second-order nonlinear differential equations with damping

Some new oscillation criteria are established for the nonlinear damped differential equation (r(t)y ) + p(t)y + q(t)f (y) = 0 that are different from most known ones in the sense that they are based on a class of new functions Φ(t, s, r) defined in the sequel. Our results are sharper than some previous results which can be seen by the examples at the end of this paper.  2003 Elsevier Inc. All rights reserved.