PERESTYUK, N. A.; SLYUSARCHUK, V. Yu. Green–Samoilenko operator in the theory of invariant sets of nonlinear differential equations. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 61, n. 7, p. 948–957, 2009. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/3069. Acesso em: 5 dec. 2025.