To cite package ‘polymatching’ in publications use:

  Nattino G, Lu B, Song C, Xiang H (2025). _polymatching: A Matching
  Algorithm for Designs with Multiple Groups_. R package version 1.0.1,
  <https://CRAN.R-project.org/package=polymatching>.

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {polymatching: A Matching Algorithm for Designs with Multiple Groups},
    author = {Giovanni Nattino and Bo Lu and Chi Song and Henry Xiang},
    year = {2025},
    note = {R package version 1.0.1},
    url = {https://CRAN.R-project.org/package=polymatching},
  }