To cite 'specr' in publications use:

  Masur, Philipp K. & Scharkow, M. (2020). specr: Conducting and
  Visualizing Specification Curve Analyses. Available from
  https://CRAN.R-project.org/package=specr.

A BibTeX entry for LaTeX users is

  @Misc{,
    title = {specr: Conducting and Visualizing Specification Curve Analyses (Version 1.0.1)},
    author = {Philipp K. Masur and Michael Scharkow},
    year = {2020},
    url = {https://CRAN.R-project.org/package=specr},
  }