Kindly cite the hetu R package as follows:

  Pyry Kantanen, Mans Magnusson, Jussi Paananen and Leo Lahti (rOpenGov
  2022). hetu: Structural Handling of Finnish Personal Identity Codes.
  R package version 1.0.7 URL: http://github.com/rOpenGov/hetu

A BibTeX entry for LaTeX users is

  @Misc{,
    title = {hetu: Structural Handling of Finnish Personal Identity Codes},
    author = {Pyry Kantanen and Mans Magnusson and Jussi Paananen and Leo Lahti},
    url = {https://github.com/rOpenGov/hetu},
    year = {2022},
    note = {R package version 1.0.7},
  }

Many thanks for all contributors!