Kenny Qili Zhu Ziwei Liu Population Diversity in Permutation-Based Genetic Algorithm. 537-547 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=3201&spage=537 2004 conf/ecml/2004 ECML db/conf/ecml/ecml2004.html#ZhuL04