To cite palmtree in publications use:

Heidi Seibold, Torsten Hothorn, Achim Zeileis (2016). Generalised Linear Model Trees with Global Additive Effects. arXiv 1612.07498. arXiv.org E-Print Archive. URL http://arxiv.org/abs/1612.07498

Corresponding BibTeX entry:

  @TechReport{,
    title = {Generalised Linear Model Trees with Global Additive
      Effects},
    author = {Heidi Seibold and Torsten Hothorn and Achim Zeileis},
    institution = {arXiv.org E-Print Archive},
    year = {2016},
    type = {arXiv},
    number = {1612.07498},
    month = {February},
    url = {http://arxiv.org/abs/1612.07498},
  }