Analysis of multivariate dichotomous and polytomous data using latent trait
models under the Item Response Theory approach. It includes the Rasch, the
Two-Parameter Logistic, the Birnbaum's Three-Parameter, the Graded Response,
and the Generalized Partial Credit Models.

WWW: https://cran.r-project.org/package=ltm
WWW: https://github.com/drizopoulos/ltm
