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

Corresponding BibTeX entry:

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