Patrick Sturm 3D-Color-Structure-Code - A New Non-plainness Island Hierarchy. 109-116 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=3045&spage=109 2004 conf/iccsa/2004-3 ICCSA (3) db/conf/iccsa/iccsa2004-3.html#Sturm04