To cite spqdata in publications use:

Ruiz M, Lopez F, Páez A (2010). “Testing for spatial association of qualitative data using symbolic dynamics.” Journal of Geographical Systems, 12(3), 281-309. 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 Páez},
    journal = {Journal of Geographical Systems},
    year = {2010},
    volume = {12},
    number = {3},
    pages = {281-309},
    url = {https://doi.org/10.1007/s10109-009-0100-1},
  }