1. [1] T. A. Canturija, Onmonotone and oscillatory solutions of higher order ordinary differential equations, Ann.Polon. Math. 37 (1980), 93-111. (Russian)
2. [2] L. S. Chen and C. C.Yeh, A comparison theorem for general «-th order functional differential nonlinear equations with deviating arguments, Atti Accad. Naz.Lincei Rend. Sci. Fis. Mat.Natur. 62 (1977), 168-172.
3. [3] L. S. Chen andC. C.Yeh, Onoscillation of solutions of higher order differential retarded inequalities, Houston J. Math. 5 (1979), 37-40.
4. [4] L. S. Chen and C. C.Yeh, Oscillation criteria for arbitrary order nonlinear inequalities with deviating arguments, Boll. Un. Mat.Ital. C 1 (1982), 279-284.
5. [5] K.Foster, Criteria for oscillation and growth of nonoscillatory solutions of forced differential equations of even order, J. Differential Equations 20(1976), 115-132.