To cite spqdata in publications use:

Ruiz M, López FA, A Páez. (2010). Testing for spatial association of qualitative data using symbolic dynamics. Journal of Geographical Systems. 12 (3) 281-309 URL https://doi.org/10.1007/s10109-009-0100-1.

Corresponding BibTeX entry:

  @Article{,
    title = {Testing for spatial association of qualitative data using
      symbolic dynamics},
    author = {Manuel Ruiz and Fernando Lopez and Antonio Paez},
    journal = {Journal of Geographical Systems},
    year = {2010},
    volume = {12},
    number = {3},
    pages = {281--309},
    url = {https://doi.org/10.1007/s10109-009-0100-1},
  }