To cite SpatialPack in publications use:

Vallejos, R., Osorio, F., Bevilacqua, M. (2018+). Spatial Relationships Between Two Georeferenced Variables: with Applications in R. Springer, New York.

Corresponding BibTeX entry:

  @Book{,
    title = {Spatial Relationships Between Two Georeferenced Variables:
      with Applications in R},
    author = {R. Vallejos and F. Osorio and M. Bevilacqua},
    publisher = {Springer},
    address = {New York},
    year = {2018},
    url = {http://srb2gv.mat.utfsm.cl},
  }