Please cite gpboost including its version as

Fabio Sigrist, Tim Gyger, Pascal Kuendig (2021). “gpboost: Combining Tree-Boosting with Gaussian Process and Mixed Effects Models.” R package version 1.5.5, https://github.com/fabsig/GPBoost.

Corresponding BibTeX entry:

  @Misc{sigrist2021gpboost,
    title = {gpboost: Combining Tree-Boosting with Gaussian Process and
      Mixed Effects Models},
    author = {{Fabio Sigrist} and {Tim Gyger} and {Pascal Kuendig}},
    note = {R package version 1.5.5},
    year = {2021},
    url = {https://github.com/fabsig/GPBoost},
  }