DAOUIA, Abdelaati; LAURENT, Thibault; NOH, Hohsuk. npbr: A Package for Nonparametric Boundary Regression in R. Journal of Statistical Software, [S. l.], v. 79, n. 9, p. 1–43, 2017. DOI: 10.18637/jss.v079.i09. Disponível em: https://www.jstatsoft.org/index.php/jss/article/view/v079i09. Acesso em: 9 apr. 2025.