Tüze Kuyucu Martin Trefzer Andrew J. Greensted Julian Francis Miller Andy M. Tyrrell Fitness functions for the unconstrained evolution of digital circuits. 2584-2591 2008 IEEE Congress on Evolutionary Computation http://dx.doi.org/10.1109/CEC.2008.4631145 conf/cec/2008 db/conf/cec/cec2008.html#KuyucuTGMT08