To cite spacetime in publications use:

Pebesma E (2012). “spacetime: Spatio-Temporal Data in R.” Journal of Statistical Software, 51(7), 1–30. https://www.jstatsoft.org/v51/i07/.

Bivand RS, Pebesma E, Gomez-Rubio V (2013). Applied spatial data analysis with R, Second edition. Springer, NY. https://asdar-book.org/.

Corresponding BibTeX entries:

  @Article{,
    title = {{spacetime}: Spatio-Temporal Data in {R}},
    author = {Edzer Pebesma},
    journal = {Journal of Statistical Software},
    year = {2012},
    volume = {51},
    number = {7},
    pages = {1--30},
    url = {https://www.jstatsoft.org/v51/i07/},
  }

  @Book{,
    author = {Roger S. Bivand and Edzer Pebesma and Virgilio
      Gomez-Rubio},
    title = {Applied spatial data analysis with {R}, Second edition},
    year = {2013},
    publisher = {Springer, NY},
    url = {https://asdar-book.org/},
  }