Changes by: Alexei Kopylov (kopylov at cs.caltech.edu)
Date: 2006-04-01 22:54:06 -0800 (Sat, 01 Apr 2006)
Revision: 8991
Log message:

      Now I define Sequent<--> Sequent{0}. I did not make it as iform, because it would break a lot of proofs