Nikos Loukeris Yiannis S. Boutalis Avi Arampatzis S. Livanis Lysimachos Maltoudoglou Computational intelligence in optimal portfolio selection - The PI model. 1-6 2015 IISA https://doi.org/10.1109/IISA.2015.7388004 conf/iisa/2015 db/conf/iisa/iisa2015.html#LoukerisBALM15