SAJAVIČIUS, S. On the eigenvalue problems for differential operators with coupled boundary conditions. Nonlinear Analysis: Modelling and Control, [S. l.], v. 15, n. 4, p. 493–500, 2010. DOI: 10.15388/NA.15.4.14320. Disponível em: https://www.journals.vu.lt/nonlinear-analysis/article/view/14320.. Acesso em: 17 may. 2024.