To cite package ‘MaddisonData’ in publications use:

  Graves S (2025). “Maddison Project Data.”
  <https://cran.r-project.org/package=MaddisonData>.

A BibTeX entry for LaTeX users is

  @Misc{,
    title = {Maddison Project Data},
    author = {Spencer Graves},
    year = {2025},
    url = {https://cran.r-project.org/package=MaddisonData},
  }