To cite the ridge package, use:

Cule E, Moritz S, Frankowski D (2020). ridge: Ridge Regression with Automatic Selection of the Penalty Parameter. R package version 2.5, https://CRAN.R-project.org/package=ridge.

Corresponding BibTeX entry:

  @Manual{,
    title = {ridge: Ridge Regression with Automatic Selection of the
      Penalty Parameter},
    author = {Erika Cule and Steffen Moritz and Dan Frankowski},
    year = {2020},
    note = {R package version 2.5},
    url = {https://CRAN.R-project.org/package=ridge},
  }