J. Adrian Zimmer Graph Theoretical Indicators and Refactoring. 62-72 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=2753&spage=62 2003 conf/xpu/2003xpu XP/Agile Universe db/conf/xpu/xpu2003.html#Zimmer03