To cite 'units' in publications use:

Pebesma E, Mailund T, Hiebert J (2016). “Measurement Units in R.” R Journal, 8(2), 486–494. doi:10.32614/RJ-2016-061.

Corresponding BibTeX entry:

  @Article{,
    title = {Measurement Units in {R}},
    author = {Edzer Pebesma and Thomas Mailund and James Hiebert},
    year = {2016},
    journal = {R Journal},
    doi = {10.32614/RJ-2016-061},
    pages = {486--494},
    volume = {8},
    number = {2},
  }