Pasi Lehtimäki Kimmo Raivio Olli Simula Self-Organizing Operator Maps in Complex System Analysis. 622-629 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=2714&spage=622 2003 conf/icann/2003 ICANN db/conf/icann/icann2003.html#LehtimakiRS03