1. Garey, M. R. and Johnson, D. S.: Computers and Intractability: A Guide to the Theory of NP Completeness. W. H. Freeman & Co., NewY ork (1979)
2. Colorni, A., Dorigo, M. and Maniezzo, V.: Distributed Optimization by Ant Colonies. In: Varela, F. and Bourgine, P. (Eds.): Proc. Europ. Conf. Artificial Life. Elsevier, Amsterdam (1991)
3. Costa, D. and Hertz, A.: Ants can colour graphs. Journal of the Operational Research Society 48(3) (1997) 295–305
4. Stützle, T. and Dorigo, M.: ACO Algorithms for the Quadratic Assignment Problem. In: Corne, D., Dorigo, M. and Glover, F. (Eds.): NewIdeas in Optimization. Mc Graw-Hill, London (1999)
5. Dorigo, M. and Gambardella, L. M.: Ant Colony System: A cooperative learning approach to the Travelling Salesman Problem. IEEE Transactions on Evolutionary Computation 1(1) (1997) 53–66