To cite package sp in publications use:

  Pebesma E, Bivand R (2005). “Classes and methods for spatial data in
  R.” _R News_, *5*(2), 9-13. <https://CRAN.R-project.org/doc/Rnews/>.

A BibTeX entry for LaTeX users is

  @Article{,
    author = {Edzer J. Pebesma and Roger Bivand},
    title = {Classes and methods for spatial data in {R}},
    journal = {R News},
    year = {2005},
    volume = {5},
    number = {2},
    pages = {9--13},
    month = {November},
    url = {https://CRAN.R-project.org/doc/Rnews/},
  }

  Bivand R, Pebesma E, Gomez-Rubio V (2013). _Applied spatial data
  analysis with R, Second edition_. Springer, NY.
  <https://asdar-book.org/>.

A BibTeX entry for LaTeX users is

  @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/},
  }
