The contribution of Nikola Obreshkoff to the theory of diophantine approximation. Annual of Sofia University St. Kliment Ohridski. Faculty of Mathematics and Informatics, [S. l.], v. 89, p. 47–58, 1997. Disponível em: https://annual.uni-sofia.bg/index.php/fmi/article/view/354. Acesso em: 14 dec. 2025.