GRITSANS, Armands; YERMACHENKO, Inara. On the maximum number of period annuli for second order conservative equations. Mathematical Modelling and Analysis, [S. l.], v. 26, n. 4, p. 612–630, 2021. DOI: 10.3846/mma.2021.13979. Disponível em: https://journals.vilniustech.lt/index.php/MMA/article/view/13979. Acesso em: 10 may. 2025.