Daniel Merkle Martin Middendorf Competition Controlled Pheromone Update for Ant Colony Optimization. 95-105 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=3172&spage=95 2004 conf/antsw/2004 ANTS Workshop db/conf/antsw/antsw2004.html#MerkleM04