To cite the ordinal-package in publications use:

Christensen RHB (2019). “ordinal—Regression Models for Ordinal Data .” R package version 2019.12-10. https://CRAN.R-project.org/package=ordinal.

Corresponding BibTeX entry:

  @Misc{,
    title = {ordinal---Regression Models for Ordinal Data },
    author = {R. H. B. Christensen},
    year = {2019},
    note = {R package version 2019.12-10.
      https://CRAN.R-project.org/package=ordinal},
  }