Nakonechna, S.O. (1998) “On the application of approximation of the central manifold of a stationary point to one critical case”,
Ukrains’kyi Matematychnyi Zhurnal, 50(3), pp. 430–432. Available at:
https://umj.imath.kiev.ua/index.php/umj/article/view/4944 (Accessed: 7 April 2025).