TONKOV, T. The contribution of Nikola Obreshkoff to the theory of diophantine approximation. Ann. Sofia Univ. Fac. Math. and Inf., [S. l.], v. 89, p. 47–58, 1997. Disponível em: https://admin.uni-sofia.bg/index.php/fmi/article/view/354. Acesso em: 15 jan. 2025.