To cite package ‘xtable’ in publications use:

  Dahl D, Scott D, Roosen C, Magnusson A, Swinton J (2020). _xtable:
  Export Tables to LaTeX or HTML_. R package version 1.8-6,
  <https://r-forge.r-project.org/projects/xtable>.

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {xtable: Export Tables to LaTeX or HTML},
    author = {David B. Dahl and David Scott and Charles Roosen and Arni Magnusson and Jonathan Swinton},
    year = {2020},
    note = {R package version 1.8-6},
    url = {https://r-forge.r-project.org/projects/xtable},
  }