Lipchan, V. V. (1996) “On the existence of an invariant manifold for weakly nonlinear matrix differential equations”, Ukrains’kyi Matematychnyi Zhurnal, 48(3), pp. 422-424. Available at: https://umj.imath.kiev.ua/index.php/umj/article/view/5340 (Accessed: 18May2024).