Meyer, David, Achim Zeileis, and Kurt Hornik. “The Strucplot Framework: Visualizing Multi-Way Contingency Tables With Vcd”. Journal of Statistical Software 17, no. 3 (October 19, 2006): 1–48. Accessed March 28, 2024. https://www.jstatsoft.org/index.php/jss/article/view/v017i03.