STOLL, H.; KING, G.; ZENG, L. WhatIF: R Software for Evaluating Counterfactuals. Journal of Statistical Software, [S. l.], v. 15, n. 4, p. 1–18, 2005. DOI: 10.18637/jss.v015.i04. Disponível em: https://www.jstatsoft.org/index.php/jss/article/view/v015i04. Acesso em: 17 aug. 2022.