On λ-stability of one essentially nonlinear nonautonomous second order equation. Neliniini Kolyvannya, [S. l.], v. 4, n. 4, p. 547–559, 2001. Disponível em: https://twinhead.imath.kiev.ua/index.php/nosc/article/view/194. Acesso em: 22 jan. 2026.