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2. Ballieu, R.J., Peiffer, K.: Attractivity of the origin for the equation
$$\ddot{x}+f(t, x, \dot{x})|\dot{x}|^\alpha \dot{x}+g(x)=0$$
x
¨
+
f
(
t
,
x
,
x
˙
)
|
x
˙
|
α
x
˙
+
g
(
x
)
=
0
. J. Math. Anal. Appl. 65, 321–332 (1978)
3. Hardy, G.H., Littlewood, J.E., Pólya, G.: Inequalities, 2d edn. University Press, Cambridge (1952)
4. Hartman, P.: Ordinary Differential Equations. Birkhäuser, Boston (1982)
5. Hatvani, L.: A generalization of the Barbashin-Krasovskij theorems to the partial stability in nonautonomous systems. In: Farkas, M. (ed.) Qualitative Theory of Differential Equations, Vol. I, II (Szeged, 1979), 381–409, Colloq. Math. Soc. János Bolyai, vol. 30, North-Holland, Amsterdam-New York (1981)