Ilan Beer Shoham Ben-David Cindy Eisner Yoav Rodeh Efficient Detection of Vacuity in ACTL Formulaas. 279-290 1997 conf/cav/1997 CAV db/conf/cav/cav97.html#BeerBER97 http://dx.doi.org/10.1007/3-540-63166-6_28