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.zurnalai.vu.lt/LMJ/article/view/20742. Acesso em: 8 jun. 2025.