BURSKII, V. P. On equivariant extensions of a differential operator by the example of the Laplace operator in a circle. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 51, n. 2, p. 158–169, 1999. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/4595. Acesso em: 5 dec. 2025.