Marc Boyer Mihaela Sighireanu Synthesis and Verification of Constraints in the PGM Protocol. 264-281 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=2805&spage=264 2003 conf/fm/2003 FME db/conf/fm/fme2003.html#BoyerS03