@Article{baldassarre03:_evolv_mobil_robot_able_displ_collec_behav, author = {Baldassarre, G. and Nolfi, S. and Parisi, D.}, title = {Evolving Mobile Robots Able to Display Collective Behaviour}, journal = {Artificial Life}, year = 2003, volume = 9, number = 3, pages = {255-267} }