KHACHATRYAN, A. Kh.; KHACHATRYAN, Kh. A. Letter to the Editor. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 62, n. 6, p. 865, 2010. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/2919. Acesso em: 5 dec. 2025.