"Necessary and sufficient conditions for oscillation of second-order differential equation with several delays"
"Necessary and sufficient conditions for oscillation of second-order differential equation with several delays"
"In this paper, necessary and sufficient conditions are establish of the solutions to second-order delay differential equations of the form \begin{equation} \Big(r(t)\big(x'(t)\big)^\gamma\Big)' +\sum_{i=1}^m q_i(t)f_i\big(x(\sigma_i(t))\big)=0 \text{ for } t \geq t_0,\notag \end{equation} We consider two cases when $f_i(u)/u^\beta$ is non-increasing for $\beta<\gamma$, and non-decreasing for $\beta>\gamma$ where $\beta$ and $\gamma$ are …