EGORCHENKO, I. A. Differential invariants of the Euclidian algebra . Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 42, n. 6, p. 767–772, 1990. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/8833. Acesso em: 7 apr. 2025.