J. Koza, S. Al-Sakran, and L. Jones. Genetic Programming Theory and Practice IV, volume 5 of Genetic and Evolutionary Computation, chapter 4, Springer, Ann Arbor, (11-13 May 2006)
J. Koza, L. Jones, M. Keane, and M. Streeter. Genetic Programming Theory and Practice II, chapter 8, Springer, Ann Arbor, pages missing?.(13-15 May 2004)