Ahmed Bouajjani Jean-Claude Fernandez Susanne Graf Carlos Rodriguez Joseph Sifakis Safety for Branching Time Semantics. 76-92 1991 conf/icalp/1991 ICALP db/conf/icalp/icalp91.html#BouajjaniFGRS91 http://dx.doi.org/10.1007/3-540-54233-7_126