1. Research Group on Natural Computing, Universidad de Sevilla, Seville, Spain. mdelamor@us.es
2. University of Minnesota, Minneapolis-St. Paul, United States. mgarciaquismondo@us.es
3. Research Group on Natural Computing, Universidad de Sevilla, Seville, Spain. {lfmaciasr,lvalencia,ariscosn,marper}@us.es