To cite partykit in publications use:

Torsten Hothorn, Achim Zeileis (2014). partykit: A Modular Toolkit for Recursive Partytioning in R. Working Paper 2014-10. Working Papers in Economics and Statistics, Research Platform Empirical and Experimental Economics, Universitaet Innsbruck. URL http://EconPapers.RePEc.org/RePEc:inn:wpaper:2014-10

If ctree() is used additionally cite:

Torsten Hothorn, Kurt Hornik and Achim Zeileis (2006). Unbiased Recursive Partitioning: A Conditional Inference Framework. Journal of Computational and Graphical Statistics, 15(3), 651--674.

If mob() is used additionally cite:

Achim Zeileis, Torsten Hothorn and Kurt Hornik (2008). Model-Based Recursive Partitioning. Journal of Computational and Graphical Statistics, 17(2), 492--514.

Corresponding BibTeX entries:

  @TechReport{,
    title = {{partykit}: A Modular Toolkit for Recursive Partytioning
      in {R}},
    author = {Torsten Hothorn and Achim Zeileis},
    institution = {Working Papers in Economics and Statistics, Research
      Platform Empirical and Experimental Economics, Universit\"at
      Innsbruck},
    year = {2014},
    type = {Working Paper},
    number = {2014-10},
    month = {March},
    url = {http://EconPapers.RePEc.org/RePEc:inn:wpaper:2014-10},
  }
  @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},
    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},
    pages = {492--514},
  }