To cite package ‘swirlify’ in publications use:

Kross S, Carchedi N (2019). swirlify: A Toolbox for Writing 'swirl' Courses. R package version 0.5.3, https://CRAN.R-project.org/package=swirlify.

Corresponding BibTeX entry:

  @Manual{,
    title = {swirlify: A Toolbox for Writing 'swirl' Courses},
    author = {Sean Kross and Nick Carchedi},
    year = {2019},
    note = {R package version 0.5.3},
    url = {https://CRAN.R-project.org/package=swirlify},
  }