[1] |
Glazman, I. M.: Direct methods of qualitative spectral analysis of singular differential operators. (1965) · Zbl 0143.36505 |
[2] |
Hille, E.: Nonoscillation theorems. Trans. amer. Math. soc. 64, 234-252 (1948) · Zbl 0031.35402 |
[3] |
Hinton, D. B.: A criterion for n-n oscillations in differential equations or order 2n. Proc. amer. Math. soc. 19, 511-518 (1968) · Zbl 0157.15001 |
[4] |
Leighton, W.: On self-adjoint differential equations of second order. J. London math. Soc. 27, 37-47 (1952) · Zbl 0048.06503 |
[5] |
Lewis, R. T.: The existence of conjugate points for self-adjoint differential equations of even order. Proc. amer. Math. soc. 56, 162-166 (1976) · Zbl 0294.34004 |
[6] |
Lewis, R. T.: Conjugate points of vector-matrix differential equations. Trans. amer. Math. soc. 231, 167-178 (1977) · Zbl 0366.34022 |
[7] |
Polya, G.: On the mean-value theorem corresponding to a given linear homogeneous differential equation. Trans. amer. Math. soc. 24, 312-324 (1922) |
[8] |
Reid, W. T.: Riccati matrix differential equations and nonoscillation criteria for associated systems. Pacific J. Math. 13, 665-685 (1963) · Zbl 0119.07401 |
[9] |
Wintner, A.: A criterion of oscillatory stability. Quart. appl. Math. 7, 115-117 (1949) · Zbl 0032.34801 |