Andrea Emilio Rizzoli Roberto Montemanni Enzo Lucibello Luca Maria Gambardella Ant colony optimization for real-world vehicle routing problems. 135-151 2007 1 Swarm Intelligence 2 http://dx.doi.org/10.1007/s11721-007-0005-x db/journals/swarm/swarm1.html#RizzoliMLG07