KALCHUK, I. V. Approximation of ( ψ, β )-differentiable functions defined on the real axis by Weierstrass operators. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 59, n. 9, p. 1201–1220, 2007. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/3382. Acesso em: 17 apr. 2025.