A note on linear perturbations of oscillatory second order differential equations

summary:Under suitable hypotheses on $\gamma (t)$, $\lambda (t)$, $q(t)$ we prove some stability results which relate the asymptotic behavior of the solutions of $u^{\prime \prime }+ \gamma (t)u^{\prime }+\big (q(t)+ \lambda (t)\big )u=0$ to the asymptotic behavior of the solutions of $u^{\prime \prime }+ q(t)u=0$