To cite variables in publications use:

Torsten Hothorn (2018). Most Likely Transformations: The mlt Package. Journal of Statistical Software, forthcoming.

Corresponding BibTeX entry:

  @Article{,
    title = {Most Likely Transformations: The mlt Package},
    author = {Torsten Hothorn},
    journal = {Journal of Statistical Software},
    year = {2018},
  }