RUSEV, P. Complete systems of Tricomi functions in spaces of holomorphic functions. Ann. Sofia Univ. Fac. Math. and Inf., [S. l.], v. 88, p. 401–407, 1996. Disponível em: https://annual.uni-sofia.bg/index.php/fmi/article/view/396. Acesso em: 24 nov. 2024.