C. Lee, and P. Cunningham. 2012 International Conference on Advances in Social Networks Analysis and Mining (ASONAM 2012), page 691--695. IEEE, (Aug 12, 2012)
L. Spector, and J. Klein. Genetic Programming Theory and Practice III, volume 9 of Genetic Programming, chapter 8, Springer, Ann Arbor, (12-14 May 2005)