Kindly cite the hetu R package as follows:

  (C) Tuomo Nieminen, Leo Lahti (2020).  R package for THL Open API
  (openthl).  URL: http://github.com/rOpenGov/openthl

A BibTeX entry for LaTeX users is

  @Misc{,
    title = {R package for THL Open API (openthl)},
    author = {Tuomo Nieminen and Leo Lahti},
    year = {2020},
  }

Many thanks for all contributors!