To cite package ‘vecsets’ in publications use:

Witthoft C (2023). vecsets: Like Set Tools in 'Base' Package but Keeps Duplicate Elements. R package version 1.4, https://CRAN.R-project.org/package=vecsets.

Corresponding BibTeX entry:

  @Manual{,
    title = {vecsets: Like Set Tools in 'Base' Package but Keeps
      Duplicate Elements},
    author = {Carl Witthoft},
    year = {2023},
    note = {R package version 1.4},
    url = {https://CRAN.R-project.org/package=vecsets},
  }