KARAPETYAN, G.; TANANYAN, H. The small parameter method for regular linear differential equations on unbounded domains. Eurasian Mathematical Journal, [S. l.], v. 4, n. 2, p. 23–35, 2013. Disponível em: https://emj.enu.kz/index.php/main/article/view/509. Acesso em: 31 oct. 2025.