POTAPENKO, I. V. New equations of infinitesimal deformations of surfaces in $E_3$. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 62, n. 2, p. 199–202, 2010. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/2856. Acesso em: 27 apr. 2025.