A. Lindgren, and K. Eriksson. Proceedings of the Ninth International Conference on the Simulation and Synthesis of Living Systems, ALIFE'9, page 456. Boston, (12-15 09 2004)
E. Shutova. Human Language Technologies: The 2010 Annual Conference of the North American Chapter of the Association for Computational Linguistics, page 1029--1037. Stroudsburg, PA, USA, Association for Computational Linguistics, (2010)