dorigo\1996 dorigo Heuristics from nature for hard combinatorial optimization problems.pdf ......\1997 M.dorigo Ant colony system a cooperative learning approach to the traveling salesman problem.pdf ......\dorigo Ant Colony Optimization.pdf ......\M. Dorigo Ant colony optimization theory A survey.pdf ......\Marco Dorigo ACO.pdf ......\The Ant System Optimization by a Colony of Cooperation Agents.pdf dorigo