To cite tfse use:

Kearney MW (2018). tfse: Various Useful Functions. R package version 0.4.1, https://tfse.mikewk.com.

Corresponding BibTeX entry:

  @Manual{tfse-package,
    title = {tfse: Various Useful Functions},
    author = {Michael W. Kearney},
    year = {2018},
    note = {R package version 0.4.1},
    url = {https://tfse.mikewk.com},
  }