To cite MPTinR in publications use:

Henrik Singmann & David Kellen (2013). MPTinR: Analysis of Multinomial Processing Tree models in R. Behavior Research Methods, 45(2), 560--575. doi:10.3758/s13428-012-0259-0

Corresponding BibTeX entry:

  @Article{,
    title = {{MPTinR:} Analysis of multinomial processing tree models
      in R},
    author = {Henrik Singmann and David Kellen},
    journal = {Behavior Research Methods},
    year = {2013},
    volume = {45},
    number = {2},
    pages = {560--575},
    doi = {10.3758/s13428-012-0259-0},
    url = {http://link.springer.com/article/10.3758/s13428-012-0259-0},
  }