To cite the spsurvey package in publications use:

Dumelle M, Kincaid TM, Olsen AR, Weber MH (2021). spsurvey: Spatial Sampling Design and Analysis. R package version 5.0.1.

Corresponding BibTeX entry:

  @Manual{,
    title = {spsurvey: Spatial Sampling Design and Analysis},
    author = {Michael Dumelle and Thomas M. Kincaid and Anthony R.
      Olsen and Marc H. Weber},
    year = {2021},
    note = {R package version 5.0.1},
  }