Note on Wong's paper
The author considers the second-order nonlinear differential equation with damping term \[ x''+p(t)x'+q(t)f(x)=0,\quad t\geq t_0, \] where \(p,q \in C[t_0, \infty)\) and are allowed to assume \(\int_{t_0}^\infty q(s) ds=-\infty\); \(f\in C^1(\mathbb{R})\), \(xf(x)>0\) whenever \(x\neq 0\) and satisfies \(f'(x)\geq \kappa>0\) for all \(x\in \mathbb{R}\). By employing the integral average technique, new interval oscillation criteria are obtained and they improve results due to \textit{James S. W. Wong} [J. Math. Anal. Appl. 258, 244-257 (2001; Zbl 0987.34024)]. The related results can be found in the paper of \textit{W.-T. Li} and \textit{R. P. Agarwal} [Comput. Math. Appl. 40, 217-230 (2000; Zbl 0959.34026)].
scientific article; zbMATH DE number 1866638