PREOBRAGENSKY, A. On stability of generating in algebra smooth functions. Lithuanian Mathematical Journal, [S. l.], v. 9, n. 1, p. 127–129, 1969. DOI: 10.15388/LMJ.1969.20742. Disponível em: https://www.journals.vu.lt/LMJ/article/view/20742.. Acesso em: 1 may. 2024.