To cite package ‘ggthemes’ in publications use:

  Arnold J (2025). _ggthemes: Extra Themes, Scales and Geoms for
  'ggplot2'_. R package version 5.1.0.9000, ,
  <https://github.com/jrnold/ggthemes>.

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {ggthemes: Extra Themes, Scales and Geoms for 'ggplot2'},
    author = {Jeffrey B. Arnold},
    year = {2025},
    note = {R package version 5.1.0.9000, 
},
    url = {https://github.com/jrnold/ggthemes},
  }