Hanning Chen Yunlong Zhu Kunyuan Hu Tao Ku Global optimization based on hierarchical coevolution model. 1497-1504 2008 IEEE Congress on Evolutionary Computation http://dx.doi.org/10.1109/CEC.2008.4630991 conf/cec/2008 db/conf/cec/cec2008.html#ChenZHK08