HENNINGSEN, A.; HAMANN, J. D. systemfit: A Package for Estimating Systems of Simultaneous Equations in R. Journal of Statistical Software, [S. l.], v. 23, n. 4, p. 1–40, 2007. DOI: 10.18637/jss.v023.i04. Disponível em: https://www.jstatsoft.org/index.php/jss/article/view/v023i04. Acesso em: 27 nov. 2021.