[1] COLES W. Ј.-KINYON M. K.: Summability methods for oscillation of linear second order matrix differential equations. Rockу Mountain Ј. Math. 24 (1994), 19-30. MR 1270025 | Zbl 0807.34042

[2] HOWARD H. C.: Oscillation criteria for matrix differential equations. Canad. Ј. Math. 19 (1967), 184-199. MR 0212252 | Zbl 0148.07203

[3] HUANG C. C.: Oscillation and non-oscillation for second order linear differential equations. Ј. Math. Anal. Appl. 210 (1997), 712-723. MR 1453201

[4] LI W. T.-AGARWAL R. P.: Interval oscillation criteria for second order nonlinear differential equations with damping. Comput. Math. Appl. 40 (2000), 217-230. MR 1763620 | Zbl 1046.34059

[5] LI W. T.-AGARWAL R. P.: Interval oscillation criteria related to integral average technique for certain nonlinear differential equations. J. Math. Anal. Appl. 245 2000, 171-188. MR 1756583

[6] NOUSSAIR E. S.-SWANSON C. A.: Oscillation criteria for differential systems. J. Math. Anal. Appl. 36 (1971), 575-580. MR 0296417 | Zbl 0222.34008

[7] REID W. T.: Oscillation criteria for linear differential systems with complex coefficients. Pacific J. Math. 6 (1956), 733-751. MR 0084655 | Zbl 0071.30203

[8] REID W. T.: A Prufer transformation for differential systems. Pacific J. Math. 8 1958, 575-584. MR 0099474

[9] STERNBERG R. L.: Variational methods and non-oscillation theorems for systems of differential equations. Duke Math. J. 19 (1952), 311-322. MR 0048668 | Zbl 0049.18704