VISHNJAKOV, M. Constructive characteristics of some classes of smooth functions in two variables in the space C. Lithuanian Mathematical Journal, [S. l.], v. 9, n. 1, p. 36–42, 1969. DOI: 10.15388/LMJ.1969.20664. Disponível em: https://www.zurnalai.vu.lt/LMJ/article/view/20664. Acesso em: 8 jun. 2025.