To cite sparr in publications use:

Tilman M. Davies, Martin L. Hazelton, Jonathan C. Marshall (2011). sparr: Analyzing Spatial Relative Risk Using Fixed and Adaptive Kernel Density Estimation in R. Journal of Statistical Software, 39(1), 1-14. URL http://www.jstatsoft.org/v39/i01/.

Corresponding BibTeX entry:

  @Article{,
    title = {{sparr}: Analyzing Spatial Relative Risk Using Fixed and
      Adaptive Kernel Density Estimation in {R}},
    author = {Tilman M. Davies and Martin L. Hazelton and Jonathan C.
      Marshall},
    journal = {Journal of Statistical Software},
    year = {2011},
    volume = {39},
    number = {1},
    pages = {1--14},
    url = {http://www.jstatsoft.org/v39/i01/},
  }