P. Massey, J. Clark, and S. Stepney. Genetic and Evolutionary Computation -- GECCO-2004,
Part II, volume 3103 of Lecture Notes in Computer Science, page 569--580. Seattle, WA, USA, Springer-Verlag, (26-30 June 2004)
M. Amos, P. Dunne, and A. Gibbons. Genetic Programming 1998: Proceedings of the Third
Annual Conference, page 679--683. University of Wisconsin, Madison, Wisconsin, USA, Morgan Kaufmann, (22-25 July 1998)