VAN ETTEN, J. R Package gdistance: Distances and Routes on Geographical Grids. Journal of Statistical Software, [S. l.], v. 76, n. 13, p. 1–21, 2017. DOI: 10.18637/jss.v076.i13. Disponível em: https://www.jstatsoft.org/index.php/jss/article/view/v076i13. Acesso em: 5 dec. 2022.