BoichukОA. A Condition for the Existence of a Unique Green–Samoilenko Function for the Problem of Invariant Torus. Ukr. Mat. Zhurn. [Internet]. 2001Apr.25 [cited 2024Nov.24];53(4):556-9. Available from: https://umj.imath.kiev.ua/index.php/umj/article/view/4277