NIKOLOV, G. AN INEQUALITY OF DUFFIN-SCHAEFFER-SCHUR TYPE. Ann. Sofia Univ. Fac. Math. and Inf., [S. l.], v. 90, p. 109–123, 1998. Disponível em: https://annual.uni-sofia.bg/index.php/fmi/article/view/289. Acesso em: 13 apr. 2025.