Paola Bruscoli Alessio Guglielmi A Tutorial on Proof Theoretic Foundations of Logic Programming. 109-127 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=2916&spage=109 2003 conf/iclp/2003 ICLP db/conf/iclp/iclp2003.html#BruscoliG03