The author presents some oscillation criteria for the second-order nonlinear neutral delay differential equation
with , , , , , and . His results present some extended Kamenev and Philos-type theorems ensuring that every solution of this equation oscillates, and solve an open problem posed by James S. W. Wong [J. Math. Anal. Appl. 252, 342–352 (2000; Zbl 0976.34057)] to find some oscillation criteria for this neutral differential equation.