Strong oscillations for second order nonlinear functional differential equations (Q1813775)

Motivated by the study by \textit{Z. Nehari} [Trans. Am. Math. Soc. 85, 428--445 (1957; Zbl 0078.07602)] of a second-order ordinary differential equation, the author establishes some sufficient conditions guaranteeing that all solutions of the second-order functional-differential equation \[x''(t)+\lambda p(t)f(x(t),x(g(t)))=0\] are oscillatory for every positive real number \(\lambda\), where \(p(t)\) is nonnegative and continuous, \(g(t)\to\infty\) as \(t\to\infty\), and \(f\) is continuous and satisfies some other conditions.