1. A. Colorni, M. Dorigo, and V. Maniezzo. Distributed Optimization by Ant Colonies. In Proceedings of ECAL91-European Conference on Artificial Life, pages 134–142. Elsevier Publishing, 1991.
2. M. Dorigo. Optimization, Learning, and Natural Algorithms. PhD thesis, Politecnico di Milano, 1992.
3. M. Dorigo, V. Maniezzo, and A. Colorai. The Ant System: Optimization by a Colony of Cooperating Agents. IEEE Transactions on Systems, Man, and Cybernetics-Part B, 26(1):29–41, 1996.
4. H. Bersini, M. Dorigo, L. Gambardella, S. Langerman and L. Seront. Results of the First International Contest on Evolutionary Optimisation. Technical Report TR/IRIDIA/96-18, IRIDIA, Université Libre de Bruxelles, 1996.
5. M. Fischetti and P. Toth. An Additive Bounding Procedure for the Asymmetric Travelling Salesman Problem. Mathematical Programming, 53:173–197, 1992.