ON LOWER BOUNDS OF THE SECOND-ORDER DINI DIRECTIONAL DERIVATIVES. Annual of Sofia University St. Kliment Ohridski. Faculty of Mathematics and Informatics, [S. l.], v. 96, p. 163–171, 2004. Disponível em: https://annual.uni-sofia.bg/index.php/fmi/article/view/170. Acesso em: 14 dec. 2025.