TORBA, S. M. Inverse theorems in the theory of approximation of vectors in a Banach space with exponential type entire vectors. Methods of Functional Analysis and Topology, [S. l.], v. 16, n. 1, p. 69–82, 2010. Disponível em: https://zen.imath.kiev.ua/index.php/mfat/article/view/441. Acesso em: 16 dec. 2025.