To cite package ‘W3CMarkupValidator’ in publications use:

  Hornik K (2026). _W3CMarkupValidator: R Interface to W3C Markup
  Validation Services_. R package version 0.2-4,
  <https://CRAN.R-project.org/package=W3CMarkupValidator>.

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {W3CMarkupValidator: R Interface to W3C Markup Validation Services},
    author = {Kurt Hornik},
    year = {2026},
    note = {R package version 0.2-4},
    url = {https://CRAN.R-project.org/package=W3CMarkupValidator},
  }