RAMM, Alexander G. Perturbation of zero surfaces. Global Journal of Mathematical Analysis, [S. l.], v. 5, n. 1, p. 27–28, 2017. DOI: 10.14419/gjma.v5i1.7474. Disponível em: https://sciencepubco.com/index.php/GJMA/article/view/7474.. Acesso em: 18 apr. 2025.