José Júlio Alferes Federico Banti Antonio Brogi João Alexandre Leite The Refined Extension Principle for Semantics of Dynamic Logic Programming. 7-32 2005 79 Studia Logica 1 http://dx.doi.org/10.1007/s11225-005-0492-y db/journals/sLogica/sLogica79.html#AlferesBBL05