Oscillation; nonoscillation; boundary value problem; neutral equations; hyperbolic equations.
In this paper, sufficient conditions have been obtained for oscillation of solutions of a class of $n$th order linear neutral delay-differential equations. Some of these results have been used to study oscillatory behaviour of solutions of a class of boundary value problems for neutral hyperbolic partial differential equations.
 K. Gopalsamy, B.S. Lalli and B.G. Zhang: Oscillation of odd order neutral differential equations
. Czechoslovak Math. J. 42(117) (1992), 313–323. MR 1179502
 K. Gopalsamy, S.R. Grace and B.S. Lalli: Oscillation of even order neutral differential equations
. Indian J. Math. 35 (1993), 9–25. MR 1249639
 I. Györi and G. Ladas: “Oscillation Theory of Delay-Differential Equations”
. Clarendon Press, Oxford, 1991. MR 1168471
 I.T. Kiguradze: On the question of variability of solutions of nonlinear differential equations
. Differentsial’nye Uravneniya 1 (1965), 995–1006; Translation: Differential Equations 1 (1965), 773–782. MR 0194689
 G.S. Ladde, V. Lakshmikantham and B.G. Zhang: “Oscillation Theory of Differential Equations with Deviating Arguments”
. Marcel Dekker, INC, New York, 1987. MR 1017244
 N. Parhi and P.K. Mohanty: Oscillations of neutral differential equations of higher order
. Bull. Inst. Math. Acad. Sinica 24 (1996). MR 1398241
 B.G. Zhang and K. Gopalsamy: Oscillations and nonoscillations in higher order neutral equations
. J. Math. Phys. Sci. 25 (1991), 152–165. MR 1135484