KACHANOVSKY, N. A. Biorthogonal Appell-like systems in a Hilbert space. Methods of Functional Analysis and Topology, [S. l.], v. 2, n. 3, p. 36–52, 1996. Disponível em: https://zen.imath.kiev.ua/index.php/mfat/article/view/18. Acesso em: 19 dec. 2025.