KUZHEL, S. A.; GROD, A. Schrödinger operators with non-symmetric zero-range potentials. Methods of Functional Analysis and Topology, [S. l.], v. 20, n. 1, p. 34–49, 2014. Disponível em: https://zen.imath.kiev.ua/index.php/mfat/article/view/565. Acesso em: 16 dec. 2025.