[1] H. Kh. Abdullah and K. T. Al-Dosary, System oscillatory
conditions, Journal of Interdisciplinary Mathematics 8(1) (2005),
89-96.
[2] M. M. A. Al-Asher, Oscillation Properties of Certain Second Order
Nonlinear Differential Equations, M. Sc. Thesis, University of Jordan,
(1993).
[3] G. J. Butker, I. H. Frbe and A. B. Mingarelli, Riccati techniques
and variational principles in oscillation theory for linear systems,
Trans. Amer. Math. Soc. 303 (1987), 263-282.
[4] R. Byors, B. J. Harris and N. K. Kwong, Weighted means and
oscillation conditions for second order matrix differential equations,
J. Differential Equations 61 (1986), 164-177.
[5] I. Kamenev, Integral criterion for oscillation of linear
differential equations of second order, Zametki 23 (1978),
249-251.
[6] A. B. Mingarelli, On a conjecture for oscillation of second order
ordinary differential systems, Proc. Amer. Math. Soc. 82(4) (1981),
593-598.
[7] Fanwei Meng, Jizhong Wang and Zhaowen Zheng, A note on Kamenev
type theorem for second order matrix differential systems, Proc.
Amer. Math. Soc. 126(2) (1998), 391-395.
[8] D. Willett, On the oscillatory behavior of the solution of second
order linear differential equations, Ann. Polon. Math. 21 (1969),
175-194.
[9] J. Yan, A note on an oscillation criterion for an equation with
damped term, Proc. Amer. Math. Soc. 90(2) (1984), 277-280.