Hothorn, Torsten, Kurt Hornik, Mark A. van de Wiel, and Achim Zeileis. “Implementing a Class of Permutation Tests: The Coin Package”. Journal of Statistical Software 28, no. 8 (November 13, 2008): 1–23. Accessed July 3, 2022. https://www.jstatsoft.org/index.php/jss/article/view/v028i08.