ZASTAVNYI, V. P. Extension of a Function from the Exterior of an Interval to a Positive-Definite Function on the Entire Axis and an Approximation Characteristic of the Class $W_M^{r, β}$. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 55, n. 7, p. 983–990, 2003. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/3973. Acesso em: 6 dec. 2025.