MURRELL, P. Importing Vector Graphics: The grImport Package for R. Journal of Statistical Software, [S. l.], v. 30, n. 4, p. 1–37, 2009. DOI: 10.18637/jss.v030.i04. Disponível em: https://www.jstatsoft.org/index.php/jss/article/view/v030i04. Acesso em: 28 nov. 2021.