Zhelonkin, Mikhail, and Elvezio Ronchetti. “Robust Analysis of Sample Selection Models through the R Package Ssmrob”. Journal of Statistical Software 99, no. 4 (August 21, 2021): 1–35. Accessed October 17, 2021. https://www.jstatsoft.org/index.php/jss/article/view/v099i04.