FELLER, M. N. On a nonlinear equation unsolved with respect to the levy laplacian. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 48, n. 5, p. 719–721, 1996. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/5307. Acesso em: 27 apr. 2025.