1.
Lykova ОB, Boichuk AA. Construction of periodic solutions of non-linear systems in critical cases . Ukr. Mat. Zhurn. [Internet]. 1987 Dec. 29 [cited 2025 Dec. 6];40(1):62-9. Available from: https://umj.imath.kiev.ua/index.php/umj/article/view/9056