US, G. F. Dual Appel systems in Poissonian analysis. Methods of Functional Analysis and Topology, [S. l.], v. 1, n. 1, p. 93–108, 1995. Disponível em: https://zen.imath.kiev.ua/index.php/mfat/article/view/5. Acesso em: 19 dec. 2025.