R. Poli, and N. McPhee. Proceedings of the Genetic and Evolutionary
Computation Conference (GECCO-2001), page 104--111. San Francisco, California, USA, Morgan Kaufmann, (7-11 July 2001)
N. McPhee, and R. Poli. Genetic Programming, Proceedings of EuroGP'2001, volume 2038 of LNCS, page 108--125. Lake Como, Italy, Springer-Verlag, (18-20 April 2001)