To cite package ‘pm3’ in publications use:

  LIU Q (2024). _pm3: Propensity Score Matching for Unordered 3-Group
  Data_. R package version 0.2.0,
  <https://CRAN.R-project.org/package=pm3>.

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {pm3: Propensity Score Matching for Unordered 3-Group Data},
    author = {Qiang LIU},
    year = {2024},
    note = {R package version 0.2.0},
    url = {https://CRAN.R-project.org/package=pm3},
  }