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Linear Differential Transformations of the Second Order. The English Universities Press, London, (1971).
MR 0463539
[2] Borůvka O.:
Sur la périodicité de la distance des zéros intégrales de l'équation differéntielle $y'' = q(t)y$. Tensor, N. S. Vol. 26 (1972), 121-128.
MR 0340687
[3] Neuman F.:
Linear differential equations of the second order and their applications. Rediconti di Mat. 4 (1971), 559-617.
MR 0311972 |
Zbl 0227.34005