To cite package ‘w3css’ in publications use:

  Fay C (2024). _w3css: W3CSS for 'shiny'_. R package version
  0.0.0.9004, <https://github.com/thinkr-open/w3css>.

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {w3css: W3CSS for 'shiny'},
    author = {Colin Fay},
    year = {2024},
    note = {R package version 0.0.0.9004},
    url = {https://github.com/thinkr-open/w3css},
  }