M. Looks. GECCO '07: Proceedings of the 9th annual conference on
Genetic and evolutionary computation, 1, page 539--546. London, ACM Press, (7-11 July 2007)
P. Gehring, and R. Wille. Proceedings of the 14th International Conference on Conceptual Structures (ICCS 2006), volume 4068 of Lecture Notes in Computer Science, page 215-228. Springer, (2006)