Amir Pnueli Sitvanit Ruah Lenore D. Zuck Automatic Deductive Verification with Invisible Invariants. 82-97 2001 conf/tacas/2001 TACAS http://link.springer.de/link/service/series/0558/bibs/2031/20310082.htm db/conf/tacas/tacas2001.html#PnueliRZ01