R. Popp, D. Montana, R. Gassner, G. Vidaver, and S. Iyer. IEEE International Conference on Systems, Man, and
Cybernetics, 3, page 2184--2189. San Diego, CA USA, IEEE, (11-14 October 1998)
W. Langdon. Genetic Programming 1996: Proceedings of the First
Annual Conference, page 141--148. Stanford University, CA, USA, MIT Press, (28--31 July 1996)