To cite SPOT in publications use:

T. Bartz-Beielstein and M. Zaefferer (2012). A Gentle Introduction to Sequential Parameter Optimization. CIplus 2/2012. Bibliothek der Fachhochschule Koeln.

Corresponding BibTeX entry:

  @TechReport{,
    title = {A Gentle Introduction to Sequential Parameter
      Optimization},
    author = {Thomas Bartz-Beielstein and Martin Zaefferer},
    journal = {CIplus},
    number = {2},
    institution = {Bibliothek der Fachhochschule Koeln},
    year = {2012},
    url = {http://opus.bsz-bw.de/fhk/volltexte/2012/19},
  }