To cite package ‘pln’ in publications use:

  Falk CF, Joe H (2024). _pln: Polytomous Logit-Normit (Graded
  Logistic) Model Estimation_. R package version 0.2-3,
  <https://CRAN.R-project.org/package=pln>.

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {pln: Polytomous Logit-Normit (Graded Logistic) Model Estimation},
    author = {Carl F. Falk and Harry Joe},
    year = {2024},
    note = {R package version 0.2-3},
    url = {https://CRAN.R-project.org/package=pln},
  }