Torben Amtoft Anindya Banerjee Information Flow Analysis in Logical Form. 100-115 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=3148&spage=100 2004 conf/sas/2004 SAS db/conf/sas/sas2004.html#AmtoftB04