Anderson CJ, Li Z, Vermunt JK. Estimation of Models in a Rasch Family for Polytomous Items and Multiple Latent Variables. J. Stat. Soft. [Internet]. 2007 Feb. 2 [cited 2024 Apr. 25];20(6):1-36. Available from: https://www.jstatsoft.org/index.php/jss/article/view/v020i06