On the point spectrum of the Laplace operator with δ-potentials in vertices of regular polyhedron. Neliniini Kolyvannya, [S. l.], v. 7, n. 2, p. 147–154, 2004. Disponível em: https://twinhead.imath.kiev.ua/index.php/nosc/article/view/298. Acesso em: 22 jan. 2026.