To cite outsider and its sister packages in publications use:

Bennett, D.J., Hettling, H., Silvestro, D., Vos, R., Antonelli, A. (2020). “outsider: Install and run programs, outside of R, inside of R.” Journal of Open Source Software, 5(45), 2038. https://doi.org/10.21105/joss.02038.

Corresponding BibTeX entry:

  @Article{,
    title = {outsider: Install and run programs, outside of R, inside
      of R.},
    author = {{Bennett} and {D.J.} and {Hettling} and {H.} and
      {Silvestro} and {D.} and {Vos} and {R.} and {Antonelli} and
      {A.}},
    journal = {Journal of Open Source Software},
    year = {2020},
    volume = {5},
    number = {45},
    pages = {2038},
    url = {https://doi.org/10.21105/joss.02038},
  }