KONSTANTINOV, A. Yu. A class of admissible functions in the principle of invariance of wave operators. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 46, n. 3, p. 227–229, 1994. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/5758. Acesso em: 14 apr. 2025.