WIRTHS, Karl-joachim. An extremal problem for polynomials with a prescribed value at a given point of the real axis. Mathematica Scandinavica, Berkeley, CA, United States, v. 66, p. 130–140, 1990. DOI: 10.7146/math.scand.a-12297. Disponível em: https://journals.msp.org/mscand/article/view/1327. Acesso em: 24 jul. 2026.