Yonit Kesten Amir Pnueli Modularization and Abstraction: The Keys to Practical Formal Verification. 54-71 1998 conf/mfcs/1998 MFCS http://link.springer.de/link/service/series/0558/bibs/1450/14500054.htm db/conf/mfcs/mfcs98.html#KestenP98