To cite package ‘PupilPre’ in publications use:

  Kyröläinen A, Porretta V, van Rij J, Järvikivi J (2019). “PupilPre:
  Tools for Preprocessing Pupil Size Data.” Version 0.6.2, updated
  2020-03-08, <https://CRAN.R-project.org/package=PupilPre>.

A BibTeX entry for LaTeX users is

  @Misc{,
    title = {{PupilPre}: Tools for Preprocessing Pupil Size Data},
    author = {Aki-Juhani Kyröläinen and Vincent Porretta and Jacolien {van Rij} and Juhani Järvikivi},
    url = {https://CRAN.R-project.org/package=PupilPre},
    year = {2019},
    note = {Version 0.6.2, updated 2020-03-08},
  }