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[2] Ezeilo J. O. C.: A stability result for the solutions of certain third order diffeгential equation. Journal of the London math. Society 37, 1962.

[3] Ezeilo J. O. C.: On the boundedness of solutions of a certain differential equations of the third order. Journal of the London math. Soc. (3) 9, 1959. MR 0104869

[4] Opial Z.: Sur les solutions de ľéquation différentielle x" + h(x) x' + f(x) = e(t). Ann. Polon. Math. VIII. 1960. MR 0113010

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[7] Ezeilo J. O. C.: On the existence of periodic solutions of a certain third order differential equation. Proc. of the Cambridge phil. Soc. (Math. - Phys. sc), 56, 1960. MR 0121539 | Zbl 0097.29404

[8] La Salle, Lefschetz: Stability by Ljapunov’s direct Method. Academic Press, 1961.

[9] Voráček J.: Einige Bemerkungen über eine nichtlineare Differentialgleichung dritter Ordnung. Tagungsbericht aus der III. Konferenz über nichtlineare Schwingungen, Nachrichten der DAW, Berlin 1965. MR 0194672