To cite the 'sirt' package in publications use:
Robitzsch, A. (2019). sirt: Supplementary item response theory models. R package version 3.5-53. https://CRAN.R-project.org/package=sirt
Corresponding BibTeX entry:
@Manual{, title = {sirt: Supplementary item response theory models}, author = {Alexander Robitzsch}, year = {2019}, note = {R package version 3.5-53}, url = {https://CRAN.R-project.org/package=sirt}, }