Gianluigi Folino Clara Pizzuti Giandomenico Spezzano StreamGP: tracking evolving GP ensembles in distributed data streams using fractal dimension. 1751 2007 conf/gecco/2007 GECCO http://doi.acm.org/10.1145/1276958.1277301 db/conf/gecco/gecco2007.html#FolinoPS07