Mauro Bianco A High-Performance UL Factorization for the Frontal Method. 893-902 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=2667&spage=893 2003 conf/iccsa/2003-1 ICCSA (1) db/conf/iccsa/iccsa2003-1.html#Bianco03