The 13th scientific session of the mathematical commission of the T. H. Shevchenko scientific society. Neliniini Kolyvannya, [S. l.], v. 6, n. 2, p. 288–288, 2003. Disponível em: https://twinhead.imath.kiev.ua/index.php/nosc/article/view/267. Acesso em: 22 jan. 2026.