Olsbjerg, Maja, and Karl Bang Christensen. “%lrasch_mml: A SAS Macro for Marginal Maximum Likelihood Estimation in Longitudinal Polytomous Rasch Models”. Journal of Statistical Software, Code Snippets 67, no. 2 (October 7, 2015): 1–24. Accessed November 26, 2022. https://www.jstatsoft.org/index.php/jss/article/view/v067c02.