US, G. F. Functions of countable families of commuting selfadjoint operators. Methods of Functional Analysis and Topology, [S. l.], v. 3, n. 1, p. 89–97, 1997. Disponível em: https://zen.imath.kiev.ua/index.php/mfat/article/view/33. Acesso em: 19 dec. 2025.