DEGUTIS, J.; STRELICAS, Š. Existence of the eigenvalues of one differential operator dependent on parameter. Lithuanian Mathematical Journal, [S. l.], v. 11, n. 3, p. 535–556, 1971. DOI: 10.15388/LMJ.1971.21012. Disponível em: https://www.journals.vu.lt/LMJ/article/view/21012.. Acesso em: 7 may. 2024.