Andrew Hone Johnny Kelsey Optima, Extrema, and Artificial Immune Systems. 80-90 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=3239&spage=80 2004 conf/icaris/2004 ICARIS db/conf/icaris/icaris2004.html#HoneK04