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[2] Hájek O.:
Structure of dynamical systems near stable points. to appear in this journal.
MR 0177404
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[4] Немыцкий В. В., Степанов В. В.:
Качественная теория дифференциальных уравнений. Гостехиздат, Москва-Ленинград, 2-ое издание 1949.
Zbl 1152.51302
[5] Newman M. H. А.:
Elements of the Topology of Plane Sets of Points. 2nd edition, Cambridge University Press, 1954.
MR 0132534