Magis, David, and Bruno Facon. “DeltaPlotR: An R Package for Differential Item Functioning Analysis With Angoff’s Delta Plot”. Journal of Statistical Software, Code Snippets 59, no. 1 (August 13, 2014): 1–19. Accessed August 10, 2022. https://www.jstatsoft.org/index.php/jss/article/view/v059c01.