José Júlio Alferes Federico Banti Antonio Brogi João Alexandre Leite Semantics for Dynamic Logic Programming: A Principle-Based Approach. 8-20 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=2923&spage=8 2004 conf/lpnmr/2004 LPNMR db/conf/lpnmr/lpnmr2004.html#AlferesBBL04