To cite package ‘qdm’ in publications use:

Umbach N, Wickelmaier F (2014). qdm: Fitting a Quadrilateral Dissimilarity Model to Same-Different Judgments. R package version 0.1-0, https://CRAN.R-project.org/package=qdm.

Corresponding BibTeX entry:

  @Manual{,
    title = {qdm: Fitting a Quadrilateral Dissimilarity Model to
      Same-Different Judgments},
    author = {Nora Umbach and Florian Wickelmaier},
    year = {2014},
    note = {R package version 0.1-0},
    url = {https://CRAN.R-project.org/package=qdm},
  }