Joint Modeling of Access to Improved Water and Sanitation in Nigeria: A Copula-Based Generalized Joint Regression and Spatial Semiparametric Approach. International Journal of Development Mathematics (IJDM), [S. l.], v. 3, n. 3, p. 429–443, 2026. DOI: 10.62054/ijdm/0303.23. Disponível em: https://ijdm.org.ng/index.php/Journals/article/view/375.. Acesso em: 25 oct. 2026.