To cite package 'difNLR' in publications use:

Adela Drabinova, Patricia Martinkova and Karel Zvara (2016). difNLR: Detection of Dichotomous Differential Item Functioning (DIF) by Non-Linear Regression Function. R package version 0.1

Corresponding BibTeX entry:

  @Manual{,
    title = {difNLR: Detection of Dichotomous Differential Item
      Functioning (DIF) by Non-Linear Regression Function},
    author = {Adela Drabinova and Patricia Martinkova and Karel Zvara},
    year = {2016},
    note = {R package version 0.1},
  }