Dazhi Jiang Zhijian Wu Jun Zou Ming Wei Lishan Kang Algorithm based on heuristic subspace searching strategy for solving investment portfolio optimization problems. 607-611 2008 IEEE Congress on Evolutionary Computation http://dx.doi.org/10.1109/CEC.2008.4630858 conf/cec/2008 db/conf/cec/cec2008.html#JiangWZWK08