To cite package ‘xlsx’ in publications use:

Dragulescu A, Arendt C (2020). xlsx: Read, Write, Format Excel 2007 and Excel 97/2000/XP/2003 Files. R package version 0.6.5, https://CRAN.R-project.org/package=xlsx.

Corresponding BibTeX entry:

  @Manual{,
    title = {xlsx: Read, Write, Format Excel 2007 and Excel
      97/2000/XP/2003 Files},
    author = {Adrian Dragulescu and Cole Arendt},
    year = {2020},
    note = {R package version 0.6.5},
    url = {https://CRAN.R-project.org/package=xlsx},
  }