To cite the spsurvey package in publications use:

Kincaid TM, Olsen AR, Weber MH (2019). spsurvey: Spatial Survey Design and Analysis. R package version 4.1.0.

Corresponding BibTeX entry:

  @Manual{,
    title = {spsurvey: Spatial Survey Design and Analysis},
    author = {Thomas M. Kincaid and Anthony R. Olsen and Marc H.
      Weber},
    year = {2019},
    note = {R package version 4.1.0},
  }