Yanchuk, S.V. (1997) “On the behavior of solutions of the equation for components of a normal system of differential equations”,
Ukrains’kyi Matematychnyi Zhurnal, 49(10), pp. 1436–1440. Available at:
https://umj.imath.kiev.ua/index.php/umj/article/view/5142 (Accessed: 7 April 2025).