Gravity Models in R. Austrian Journal of Statistics, [S. l.], v. 47, n. 4, p. 16–35, 2018. DOI: 10.17713/ajs.v47i4.688. Disponível em: https://www.ajs.or.at/index.php/ajs/article/view/688. Acesso em: 26 may. 2026.