To cite partykit in publications use:

Hothorn T, Zeileis A (2015). “partykit: A Modular Toolkit for Recursive Partytioning in R.” Journal of Machine Learning Research, 16, 3905-3909. https://jmlr.org/papers/v16/hothorn15a.html.

If ctree() is used additionally cite:

Hothorn T, Hornik K, Zeileis A (2006). “Unbiased Recursive Partitioning: A Conditional Inference Framework.” Journal of Computational and Graphical Statistics, 15(3), 651–674. doi:10.1198/106186006X133933.

If mob() is used additionally cite:

Zeileis A, Hothorn T, Hornik K (2008). “Model-Based Recursive Partitioning.” Journal of Computational and Graphical Statistics, 17(2), 492–514. doi:10.1198/106186008X319331.

Corresponding BibTeX entries:

  @Article{,
    title = {{partykit}: A Modular Toolkit for Recursive Partytioning
      in {R}},
    author = {Torsten Hothorn and Achim Zeileis},
    journal = {Journal of Machine Learning Research},
    year = {2015},
    volume = {16},
    pages = {3905-3909},
    url = {https://jmlr.org/papers/v16/hothorn15a.html},
  }

  @Article{,
    title = {Unbiased Recursive Partitioning: A Conditional Inference
      Framework},
    author = {Torsten Hothorn and Kurt Hornik and Achim Zeileis},
    journal = {Journal of Computational and Graphical Statistics},
    year = {2006},
    volume = {15},
    number = {3},
    doi = {10.1198/106186006X133933},
    pages = {651--674},
  }

  @Article{,
    title = {Model-Based Recursive Partitioning},
    author = {Achim Zeileis and Torsten Hothorn and Kurt Hornik},
    journal = {Journal of Computational and Graphical Statistics},
    year = {2008},
    volume = {17},
    number = {2},
    doi = {10.1198/106186008X319331},
    pages = {492--514},
  }