ZEILEIS, A.; GROTHENDIECK, G. zoo: S3 Infrastructure for Regular and Irregular Time Series. Journal of Statistical Software, [S. l.], v. 14, n. 6, p. 1–27, 2005. DOI: 10.18637/jss.v014.i06. Disponível em: https://www.jstatsoft.org/index.php/jss/article/view/v014i06. Acesso em: 17 aug. 2022.